It seems to be an app issue. Liftoff doesn't really seem that smooth to me either, and my phone is not a bad phone.

Caught it jumping around earlier when a post had scrollable embedded media in it. As you bring the scrolling frame into view, the moment the top of the frame aligns with the top of the viewport, the whole feed jumps down. Not sure what it's jumping too, looked like the bottom of the scrollable area was jumping down to the bottom of the viewport. Very jarring, in any case.

It does odd things in iOS too, will pause for a fraction of a second and then jump.