Had the same problem a while ago.
Yes, it seems '-' is not allowed in unit names for recruitment to properly work. In weapon names for example it is viable.

As to 'why' I have no idea. Funnily enough, you can use German Umlaute (ä,ö,ü) in names and recruitment works just fine, although the Umlaut is replaced with a placeholder sign ingame.

Maybe some internal way, how the code uses '-' signs to organise units and using them in a name messes with that? Who knows.