How the elements are structured

All event handlers are on the colored elements. The element structure, the target of the initial event, and the recipient of pointer capture vary in each test case, as described below.

What should happen

Green, yellow, and orange should all move with the pointer if the pointer sequence starts on the colored element.
Red should never move.

What does happen (post Safari 15.5)

Green and yellow correctly follow the pointer.

Orange might not move for one event (barely noticable, except for through the console logs), Red might move for one event (noticable as a slight change in position, both conditional on the pointer remaining over the slider element.