Freeing up space · Free Up Space wizard and button
Why does the review say a folder is still being counted, or that it can't show a breakdown?
Short answer: Sizes are measured as you tick, so a big folder may still be counting — you can carry on. If a folder can't be looked into, the move still works; only the preview breakdown is unavailable.
Sizes in the review are measured the moment you tick a row, so a very large folder can take a little longer to count. Rather than make you wait, the review says it's still counting and lets you carry on.
If a folder can't be looked into at all — for example because macOS won't let any app list its contents — the review says the move will still work but it can't show you a breakdown first. That's a limit on the preview, not on the move.
You can always come back after the run: everything moved appears in What's Using Space with a Move back button. See how to move a folder back.