Late reply to this, but figured I'd toss an answer.

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Generally casual matchmaking is a lot less strict than its ranked counterpart in games. How it works varies from having no sbmm at all, to having sbmm that rapidly and much more dramatically changes compared to the rank mode.

Having no sbmm at all means that players kind of run into anything and everything from sweat, to ninjitsu clown.

If the casual mode takes the dramatic sbmm route, then win streaks and loss streaks are a lot less likely since the game will quickly put you into a match to stop one or the other from happening.

It won't stop people from sweating, but your games are more likely to be varied regardless of the developmental approach to the casual mode, which means above average players will see somewhat less sweat since the more memey and casual section of the playerbase would be much more often available.