I’m on PC, so I don’t know if what I have found is the same on XBOX. Anyway… I hope I can help someone.
After the first patch, the reverse part of the axis seems to be working, if you use Throttle axis (0 - 100%). There is still an issue on the default profile: if you modify any hardware setting on it, it is simply ignored. So what I ended doing is: 1. Duplicate default TCA Quadrant profile for planes, and assign a name of your choice. 2. Change hardware settings as follow: move neutral to 0.4 (fine tune this for your specific throttle), and increase dead zone to 0.05. Do it for axis JOISTICK LAXIS X and JOYSTICK LAXIS Y. 3. Save and back.
You should now have a nice linear response in the throttle, be able to reverse with the reverse part of the axis, and have the neutral correctly placed in the idle detent.
For aircraft that have an integrated throttle calibration (like Inibuilds ones) you can follow the same procedure but be sure to re-calibrate detents in their EFBs.