Unfortunately, I've not personally tried the bin/cue support in SheepShaver. It was added by an external contributor in this thread on b2-devel: http://sourceforge.net/mailarchive/message.php?msg_id=26341206. Perhaps you could ask him?

I agree that we shouldn't do this for cdrom/floppy since those require special handling, but that we should do it for VHD and bin/cue. I'd like the pull request to convert those two before I merge it in, else it seems kind of silly to iterate over an array that has one entry. :)