Please see the easing curves documentation at:

https://doc-snapshots.qt.io/qtsaferenderer/qtsr-animations.html#easing-curves

There is a statement:

"If the timeline animation contains an unsupported easing curve, it is replaced with a liner animation, that is, no easing curve is used."

The same applies to transition animations as well, it is not limited to the timeline animations. So could the sentence be updated? =>

"If the timeline or transition animation contains an unsupported easing curve, it is replaced with a liner animation, that is, no easing curve is used."