Interesting. I don't see the pmbmf suffix in the FileAssociations.xml, so wouldn't expect this file to be included. It may be that the file association mechanism has be modified in some way as to allow this file type, and perhaps others, be imported, since things are handled differently on the Mac.
JohnT would have to add comments.
I don't know of any way to exclude files by pattern in MC. You might try disabling all Playlist, Data, and Other ypes for the path under Tools > Import > Configure Auto-Import.