I always assumed that max in-game sense was a max potential fidelity thing (raw), and that all lower settings simply diluted the sensitivity or fidelity. Using this assumption I presumed that AA was a finite variable, and that the factors that determined the manipulation or interaction with the AA hit box were simply a sensitivity and velocity thing. Kind of like, the faster your reticle is moving, the less the AA modifier affects it's velocity, giving the impression that the AA is weaker.
I made the same assumption. But hitbox entry was more difficult at max sensitivity in Destiny 2 testing (I chose it because AA and bullet magnetism is insane in that game).
0.8 ADS multiplier at 20 in-game sens vs 0.8 ADS at 10 felt very different, with the lower sensitivity offering less resistance into the hitbox, making it feel slightly weaker but more compliant. I expected it to be the other way around, with lower sensitivity making AA stronger but harder to push into the hitbox. Increasing the ADS sensitivity multiplier did improve the AA bubble effect in D2, but 20 / 0.9 still didn't feel as good as 10 / 0.8 and it wasn't linear.
What I did find was AA strength felt roughly equivalent at 10 in-game sens at 50 NEXUS sens versus 20 in-game sens at 25 NEXUS sens. It's just the hitbox entry that differed.
Retraining STs at lower game sensitivity sounds like nightmare fuel for XIM as a decade's worth of work is down the drain and they'd lose the unified APEX & NEXUS configs. It might be worth testing for a few popular games before drawing any solid conclusions, but I can certainly see a big argument for why this shouldn't be done.
It's easy enough to muck around with in-game sens to find the right AA feel. The potential cost of doing so reduced accuracy of Smart Translation, but I haven't noticed any loss of fidelity. OBsIV tried it in Halo Infinite and the ST was no longer linear, so it's not a universal finding.
Long story short - for Apex Legends at least, it sounds like a Pro ST may be trained to see if AA behaviour does differ at lower than max in-game sens. It's an outlier though because AA is disabled at 8/8 in AL, whereas that doesn't seem to be the case in any other game.