I think what war thunder doesn’t take into an account is the “least force demanding” stick position.
And the max control force that isn’t separate for roll and pitch.
Real life aircraft with an analog stick have the “feedback”. As the aircraft changes in the speed, they move by themselves.
In that case, a pilot has to apply forces to keep the stick in the central position.
Downwash affects the tail in such a way.
Even in full real control, if you don’t add any imputs, the aircraft maintains the central stick position. Even if the game is just automatically compensating the force, meaning there is a different point of least force demanding position. Aka the position of stick you get from not holding the stick.
When the player puts 100% roll and 100 % pitch, the resulting effective force has be 50% for each.
If your gorilla pilot can exert 100kg stick force. Putting max pitch and roll should put 50kg for roll and pitch. Not 100kg + 100kg. That would be 200kg combined.
The pure roll(no pitch force) would be the same, but pitch + roll should be slower to roll unless snapping.
If you are going fast, the pilot has to be compensating by putting a force just to fly straight so the amount of force you can use to roll should be smaller even if the aircraft seems to be purely rolling.