I thought I had a bug in my project after upgrading to jQuery 3.6.0 and jQuery UI - v1.13.0 but this is reproducible with downloading the full jQuery UI as of today:

Not just hovering, but any mouse move on any of the items in the autocomplete result list clones every item inside .ui-helper-hidden-accessible DOM element. Keep going and the debug console scrollbar starts to become very small.

Is this the intention? I have some performance concerns here over cloning so many elements in a hidden DOM, therefore polluting the DOM significantly.