I just completed a test that goes even further to establish the fact that the calibration of the right thumbstick is different from that of the left. What I did was to use my "Swap Stick" Perfect Golf profile I've made for my XBox One Elite controller, such that the left thumbstick has been remapped to the right thumbstick, and vice versa. I then changed controller handedness in Perfect Golf's "Player" settings to "Left". I then set out to the practice range. On the range, I had to swing the club with the right thumbstick, even though my controller handedness was set to "Left" in Perfect Golf's settings. This is because of the stick swap I had in effect from the Elite controller App.
The results? My swingpath deviations were in the 30 to 90 degree range with the right stick, like I'd been seeing with the left thumbstick with default mapping in the last six weeks. This proves to me that the left and right thumbsticks are calibrated differently, and that Perfect Golf comes a whole lot closer to delivering the kind of performance I believe the developers intended using the default, right thumbstick calibration, no matter which thumbstick to which it is mapped. I just wish it was possible to swap the thumbsticks on all controllers by remapping them via an app, so that all left thumbstick swingers could experience Perfect Golf the way it should be experienced.