The problem with your collective misunderstanding of how this works is that you ignore, in the specific wording of the accounts, all the numerous clues that these downthrottled turns are indeed SUSTAINED...
-First of all, there is no mention in any of these accounts of UPTHROTTLING...
-I concede that downthrottling exists also for cancelling brief overshoots: The short-lived nature of those is very evident in the accounts, and often it can be achieved in other ways, like dropping flaps, side-slipping, rolling violently or, for the P-47, even firing its guns...
-I do not claim downthrottling below 250 MPH gains a far higher turn RATE: It may or may not according to type, or remain equal on some types. I claim it reduces turn RADIUS greatly. Note Karhila says "I turned equally well, but in a smaller radius".
-No explanation has been provided by anyone as to why Karhila says the "optimal" sustained turn rate (or sustained turn rate/radius combo) speed of the Me-109G-6 to be around 250 km/h, or 160 MPH(!). This is clearly far below any "Corner Speed" however it is defined. (The Fins tested an unspecified sort of optimal turn speed on the Me-109G-6 as being around 220 MPH, and Il-2 supposedly has it at 240 MPH for sustained turns on the P-51D)
That he mentions such an extremely low speed in the context of explaining his downthrottling tactics in sustained turns is undeniable... He even mention his tactics in contrast to those who throttled up! He also makes NO mention of upthrottling back up himself, and neither does any of those other sustained downthrottling accounts.
Note also his wording of the "P-51" dogfight: "I was HANGING behind him, unable to gain deflection, until he made a mistake". Meaning this was going on for quite a while... He described of this specific combat, but in another interview, that the speed of the "P-51" was 300 km/h (200 MPH) in a wider radius, while he was at 250 km/h in a smaller radius, and that the P-51's "higher" speed is what prevented him from gaining deflection: 200 MPH in a P-51 or P-40 is well below even the watered-down 10 seconds to blindness "Corner Speed" of 4-4.5 Gs...
THAT "P-51" battle, in the other interview, was clearly described as going on for "several" 360° turns near the water... This excludes any "non-sustained" explanations...
The conclusion I draw from the "P-51" speed being stated as being 200 MPH is that both were downthrottling to their optimal sustained turn rate/radius combination, but maybe because of the 20 mm gondolas the Me-109G-6 barely won despite the wingloading advantage...
I do accept that the FW-190A is incapable of matching the 160 MPH turn radius of the Me-109G-6, but I do maintain that it has a higher sustained turn rate slightly above that speed (the 109F could compete in rate, but not the G): Say something like the P-51D's preferred sustained turn speeds of 190-200 MPH, but with a better sustained turn rate than the P-51D (because of a smaller radius), and also a better sustained turn rate than most other fighters in Europe except some Russian fighters and some Spitfire Marks.
I never said downthrottling was advantageous ONLY to the FW-190A, only that it may be MORE so, because of the type's patently awful, and downright scary, high-speed handling behaviour...
Until the problem of TRACTION/PROPULSION is understood, nothing will be resolved further: In the case of ALL airborne nose-traction, I assert less is indeed more: Here is an interesting example that was presented to me on Il-2 to show me the errors of my ways: It shows a genuine understanding of my argument, but achieves the opposite of what the author intended...
Here is the argument: If what I say is true for the prop's passive resistance to turning, would it not also mean that the BAC Lightning jet would benefit in turns of lowering the power in its UPPER engine to help the turn? (It is a jet fighter with two large engines in an over-under fuselage position)
To that I say no... It merely shows how the issue here is so large it cannot be seen: Turning basically means continuously raising the leading edge of the wings (which makes the whole thing very different from climbing): What leverage does the jet engine thrust have to counter-act the raise of the leading edge of the wings? It is the other way around here: It is the wings leading edges that HAVE 15-20 ft. of leverage to deflect the thrust, not the other way around!
What if we were to modify the BAC Lightning?: Let's imagine re-routing the jet nozzles, say with no loss of thrust efficiency, so that the SAME thrust exits now out of a nozzle on each SIDE of the nose: No longer a top and bottom difference!: The thrust is now 15-20 ft AHEAD of the leading edges (say the median point of them given the sweep), and there is now no vertical separation in the thrust!
Would reducing the nose pull on such an airccraft, which has NO large flat disc to resist vertical twisting (The side-by-side nozzles have NO right-angle stress-riser vertical leverage like the flat disc prop has), would that produce an increase in sustained turn rate at lower speeds if you lowered the tractive power?
It would certainly help the wings to keep lifting their leading edges continuously, since the nose-pulling continuously pulls then down!: If they lift their leading edges easier, then it is less taxing for the wing lift to achieve this raising action: Less taxing of the wing lift means less REAL-LIFE wingloading...
So you can clearly see here the exact same thing remains true regardless of the nature of the traction: The flat prop disc's passive resistance and right-angle stress-riser leverage is only a compounding factor of an inherent nose-traction problem that can be alleviated only by reducing power in a continuous turn (short of putting the thrust at the rear!)...
All of this would be common knowledge if all jets had their exhausts exiting in the nose... All jet fighter pilots would be today taught to downthrottle in turning combat occurring BELOW Corner Speed if their jets were all nose-tracted... (And that could possibly drive combat speeds down, despite the instantaneous explosive impact of missiles, at least to some extent...) That they might be taught that their principles of fighting was refined in WWII (or even WWI!) may be nice for morale to give them a sense of connection to a glorious past, but it is completely artificial: Nose traction requires you to THINK about turning combat differently...
It is very nice to repeat like a mantra that "speed is life", but limp-wristed guns when you are going too fast are nowhere near as good as missiles (as the Komet found out), and in WWII it was the limitations of the machines that often forced a type of fighting we seem to have quickly forgotten...
Gaston