Not sure I fully understand your question, Paul. The folder (Pictures) is not changing very often... at least not by me. However the Photos Library.photoslibrary is syncing to iCloud and it is available to my spouse and daughter, so I suppose it 'syncs' and therefore changes anytime one of us take a photo that gets included in the common iCloud Photos Library.
Still, that, in my small brain, doesn't seem to account for the file being moved to trash so regularly... like every five minutes or so... Unless it just happens to be the iCloud syncing process.
I think mayhaps I should remove the Hazel sync of this particular file and, because I want a local copy, just copy or sync it separately with a time constraint. Unless, of course, you have a better solution.
Ken