Hi,
They should apply actually, the media file search inherits that from the post type search. I have tried to replicate this, but it seems to be working all right on my end. This might be a yet unknown bug, but I’m not sure how yet.
Can you please add temporary (s)FTP and back-end access so I can play around with the configuration and debug the query? I would like to debug the code to see what exactly is going on and why the field is not parsed correctly.