Yeah, that is a 50-mile long thread about moving and copying.
In my case, it's just when I'm watching the right pane in a File Manager display. The backup file being updated will sometimes auto-update its size every second or three, without me pressing F5 or clicking on the refresh button.
Other times, nothing. I must manually press F5 or refresh to see the file size increment.
Obviously, this really only applies to very large files as they're being written, such as backup images from Acronis or Macrium or another backup tool, or maybe as an ISO file is being transferred, copied, or pasted.