interesting experiment
I removed the QUIET flag so I would get the delete confirmation box,
I started a separate 5 gig file copying to my current drive just to slow things down,
Then I used the button on a folder full of files.
The move-to-parent happened (taking about 2 seconds of course)
but the delete confirmation never happened! - so delete is bailing out when there is a slow move, it seems,
I understand if it might be too dangerous to make the delete more forceful.