It's not a bug, it's simply based on the fact that clrmamepro doesn't use the 'merge' information since it was not accurate at all in the past. clrmamepro builds up valid and strict parent/clone relationships and it's also strict on that.
Each file has to be present, so if a parent/clone relationships uses different names for the same file (which shouldn't happen anyway to quote Nicola but it's used rather commonly, so blame the devs...), you need both files.
The discussion about these 'double-files' is as old as MAME and the majority of users like the cmpro way better since it gives you a more accurate look at the single splitup sets.



Roman Scherzer