A tool a only as good as the person who uses it. You can look purely at score to as deeply as run history. If someone wanted to, they can look at another persons run history or their best timed run and see who was in the group. You can tell if they were carried.
You will probably ask, who the hell is going to go through all of that effort? I do and everyone I push keys with does too.
Anyone can buy KSM, but you can’t really buy high score. People also wont be buying 10 runs on each dungeon to build up a history either. Even if they did, you can still tell.
They get carried. Now imagine if keys don’t deplete and they can continuously bring other unsuspecting victims until a group is strong enough to carry them even further.