I have a Macbook and a Mac Mini at home, connected with Universal Control. When I copy-paste some big group of files (say, 250GB of photos) the OS creates a copy of all those files under shared-clipboard in Library (filling up disk space in short time) even if I don't even move the cursor to other devices. It doesn't even delete those files and clear up disk space even after I paste it. This is a design flaw, it shouldn't be like this.
Universal Control Copy Paste Issue
Those are probably clones that don't consume any additional storage space. You can verify this in Disk Utility. Finder isn't able to see low-level storage blocks.