This doesn't make any sense
If he regularly can match with Killcat, then he can match into Master lobbies off of other data like K/D. But that also means that he shouldn't be in lobbies with actual rookies/bronze players. Unless Killcat is smurfing? Or they ignore ranks altogether, but it clearly says it usually matches you off of rank. I guess "usually" includes conveniently written plot points like this.
Like even if disconnecting in rank means he's hardstuck rookie, or constantly playing pubs instead, then Killcat has no reason to be in the lobby then right? Unless they fought in a pub?
Also, why are they fighting Killcat in a singles match if Killcat only wanted to fight ojisan?