Is this still an issue? if so, are you sure you’re using the unpin command as opposed to ⌘DEL? the unpin shortcut is ⇧⌘P.
Also, if you try export/import, it should fix issues with pins. That is per: Renaming pinned bookmarks - #4 by LucB
At the moment, if you are syncing Hook bookmarks between devices, you might need to repeat on other mac and turn off sync on both machines (This is not confirmed, but would be a precaution for this issue.)
we also recently optimized Hook window which improves performance with Pinned section (reported elsewhere).