mugann are basically something in line with zerg and kerrigan, though far weaker for the most part. just minions basically.
but it's pretty much irrelevant to anything there because it's like saying 'in order to get to kefka you need to go up the tower and beat his 4 bosses!' in the series AS is busy playing lockdown on the universe and has checks set for 'em, those weird ship-like minions being the main thing he uses to check 'em after certain conditions are met usually. which ain't really ever an issue since if he's there then hey, he's there. fight starts with him the same way a fight starts with kerrigan. whether she'd use the zerg or not is on her account, but they ain't there to start. same with him. ...'cept he wouldn't use 'em because he's already there and that ain't his style.
aka, it's a crap and nonsensical argument. big surprise.
--
The future must protect the clone's past.
"Maybe it's a tentacle, molesting the planet itself. - Aschen Brodel.