Sorry to be nitpicky, but ever since Super Whisper and 4 TIE Fighters became a thing, groups of 4-5 ships started to be called, "mini swarms". At a certain point BBBBZ came along with the 2 ship meta and now BBBBZ is considered a swarm because it doesn't have a fat turret and it has more than 2 ships in it. 5x Kirfghnbvxz is called a swarm too.
6 is the threshold for a swarm. 6 A-Wings, 6 Bombers, 6 HWKs (lol), 7 M-3A's, 4 Z-95's & 2 Starvipers, etc. are swarms. Your 4 B-Wing list with a z-95 tacked onto it isn't.