I'm not sure based on the wording in the documentation that it is a bug. I don't think it is a great feature but, hey, I'm not the author. You should see a link to the bug tracker for a module on its page at CPAN.org, though. (Edit: Ignore what I said here, and listen to anonymonk above)

clinton's File::Find::Rule looks to be a pretty sweet interface, though, that fixes your issue with prune neatly. I'd check it out.