The 120Hz was never working fully on Apple's LED displays.
For 120Hz to work properly, the pixels need to refresh at 8.3 ms or faster. For the M2 iPad Pro,
Notebookcheck clocks the pixel refresh at 37.53 ms which is 4.5x too slow. And the M1 was 45ms which is 5.5x too slow. And the 2018 iPad Pro was 54ms which is 6.5x too slow.
If you want actual 120Hz worth your money, you need to buy OLED because it's refresh is under 3ms.
(Did Apple reviewers bring this up? Most don't because they don't sufficiently involve themselves in technical details to catch hardware deficiencies)