"Recents" folder in Finder is empty
Since the answers I found on Apple Community are all older and you can't update the posts, I've created a new one because again, this slight bug has returned after the latest macOS 15.4 update. The solution I found simple (not all the terminal changes and things most novices with macOS shouldn't be playing with.) If this occurs not long after having installed a new update, shutdown the MAC and start it again.
Voilà! The folder was populated again as normal after I did this. So, I'm thinking that this might have to become SOP (Standard Operating Procedure) to do for the majority of small macOS bugs after encountered after updates, particularly major ones like 15 > 16 or 15.x > 15.x₁.
Hope this helps someone else!
iMac 24″, macOS 12.3