i don't think exchanges "support" anything. and they definitely don't give a shit about block size, scaling or in some cases even security not matter if it is about bitcoin or some shitcoin. the only thing that exchanges care about is trading volume because that is the main (legal) way they make money. which is why they haven't listed BSV because its volume was a lot lower than most of the altcoins that they also don't list. if they were to list a new one they would list one of those.
BSV gained some volume this year though so they may list it now if they think it can sustain that higher volume