I used science to verify that indeed my new ipad pro's display can jam at 120 hz.
Exhibit A: https://youbeill.in/scrap/noise-120fps.mp4
Load that up in VLC for iOS, playing back at normal speed. Then get a camera that can shoot at least 120 fps - an iphone will do. Record some video of the ipad playing the above file.
Explore the camera recording using a big computer. If you can see every frame number, you did it.
Exhibit B: https://youbeill.in/scrap/120hz-fo-sho.mp4
(sure, cam shutter and display aren't synced)