That's a good line of thinking. I'm pretty sure the best they could do is generate xpubs for potential derivation paths for that set of seed words; then, if they also happened across a multi-sig wallet descriptor backup that contained a matching xpub as one of its keys, they could then conclude that the set of seed words was indeed used as part of that particular multi-sig wallet
BTW, since a 2-of-2 would absolutely require both keys (by a single user in this case) to be useful, there wouldn't be as much reason to save a wallet descriptor backup (that someone else might happen upon) as you probably would/should for a 2-of-3, etc,