Why are you assuming linear yeilds the fastest turn speed? Exponential ramps up the turn.., err.., exponentially, resulting in a faster turn as long as it hasn't hit the turn cap. But of course it also moves away from the 1 to 1 mouse velocity to reticle movement that the ST is trying to achieve.
And anyway, there are hundreds (or possibly even thousands) of variations that can be produced by tweaking combinations of the Advanced Settings. Which one is best? Which one should a new Smart Translator be trained on? And of course, you'll get a dozen different reponses to those questions. In order to keep everybody happy, Mist would need to train a lot of new STs.
And even then, many people would still be asking for a retrain...
The in game settings which will work best are the ones that provide the most linear movement, so that with a scale of 0-100% analog movement, you get a equally distributed 0-100% turn speed in game, prior to an ST being used.
Emulating linear movement is a purpose of the ST. Any acceleration in the game will affect the output quality you get from an ST, being that you are always limited by the analog sticks 16bit/8bit resolution. If each increment from 0 and 65,535(xbox one) was equally distributed in terms of movement in game, you would have the optimal translation from mouse to analog stick movement.
That is just talking about the in game curve option.
For the turn speed specifically, there are advanced settings in apex where you can max out the pitch and yaw values too - these probably do not change the look mechanic, but it's hard to know for sure without the tools the XIM devs use.
