I'm gonna play devils advocate for both sides here.
In a previous thread, it was posted by someone from HTC that clearly stated flight models aren't adjusted for 'game play' purposes.
ack-ack
First, I sense a lack of inertial roll that doesn't seem realistic. No I don't have hard data except for a simple law of physics. Seems once a roll is initiated, no matter how fast that roll was, it quickly stops with little or no stick counter.
And the Brew is an unbelievable freak of nature.
I don't know if either is proof of anything and I don't believe it is intentional if they are off.
And i have wondered for years...why the story's i hear for years from WWII pilots don't jive with HTC's p51 model.
And back to the op, misconceptions.
First is pride. Lots of pilots said their a/c was the best ever made. Some really believed their own hype.
I've heard the same things about the pony. A lot of vets believed they could out turn any 109. I think they just never met a 109 in the right conditions that included a pilot who was skilled with the 109, who was dumb enough to get into a protracted turn fight when he was most likely outnumbered and probably a half a dozen other factors.
The 109 turns well but has nasty all around handling characteristics. The Pony had great handling characteristics all around.
IRL no one pushed the envelope without huge concern for what the consequences were. In the Mustang our guys felt comfortable pushing further. I would bet not so much in the 109.
And from what I can tell, the 109 wasn't seen as a turn fighter by the Germans. What I see is that they were always focused on speed and the fact that a couple of 109s were close in turn performance to Allied counterparts was incidental to them.