How does the porpoise do anything to spoil someone on your 6? You're just letting them gain on you, no?
In combination with rudder kicks and rolls it becomes very difficult to hit, and it lets them survive until they 1. Begin to outrun you with superior acceleration, (seen this happen with Yak3s against P-51s alot) 2. You get shot off their tail, 3. They let you get real close and then pull a better move for overshoot.
For instance, consider a P-47 making a guns pass on a Spit16, or any other typical BnZ energy vs. angles matchup. Classical ACM would call for an energy conserving break turn to spoil any tracking solution by the Jug, and an out of plane jink (roll and point the wingtip at him) if the Jug lines up a snapshot. Repeat until E states equalize and the turn fighter can take the offensive. However in this case the Jug has some time to react to the maneuver and may 1. Line up a successful gun snapshot or 2. Go vertical with extra speed and reset, against an opponent who has bled at least some of their E in a break.
Now imagine the same Jug barreling in on a Spit16 doing the land trout routine. The Spit is very difficult, sometimes nigh impossible to hit, yet it is never forced to commit to the sort of break turn that in the above example would allow either a plausible snapshot at a planform or a vertical reset. As the range closes it may finally commit to an abbreviated classical defensive maneuver, which the Jug pilot no longer has much of a window to react to. By using this maneuver the defending fighter can be nigh impossible to bring down and ALSO get a flight path overshoot while remaining on a the same heading as the attacker with more speed than if they had defended with at least 90 degrees of break turn-at least this it the energy situation if the defender is in a Spit! Read they are right in the former attacker's rear hemisphere. The former attacker has limited separation in speed now and it may be suicidal for him to go vertical at this point.
However, without the willingness or ability to rapidly go from stick-in-gut to stick-to-the firewall again and again in pitch axis, any form of stick stirring becomes far less effective. Only with a significant roll rate advantage can planes "stir" effectively, and this still isn't nearly as maddening as roll and rudder in combo with the "porpoise". By comparison, WITH the porpoise, even horrible rollers like the Typhoon can frustrate planes that roll better.
