Recent files are sorted by date, and clearing the menu item doesn’t remove the smart search from the Finder or back date those files to make them no longer recent.
If you find the smart search to be a waste of space - remove it as follows. No files are moved, changed, or deleted whether you have or remove this item in the Finder (just as no files change when you clear the menu of recent apps and files).
Hold down the Control key and select remove from the Sidebar if you don't want the finder to show a collection of the most recent files visible to your user on the Mac.
Just like a library has a catalog of all items, the Mac dates items on the filesystem and sorts them by recency by default.
If you need a different collection of files, you can make your own smart search criteria and add that instead.
Recents is just a smart folder that the system shows you by default and provides a custom icon of an analog clock.