That's not quite as trivial as you make it sound
Since ChipMixer gives you a private key, in the initial transaction you make to either sweep the coins to your own wallet or transfer them to someone else's wallet (such as depositing from an exchange), you only have to look back a single transaction and see 20 outputs all of 0.016 BTC (for example).
I also think participating in Wasabi CoinJoins is more likely to mean directly transacting with DNM outputs, which may have some relevance in cases like these.
Agree about this. CoinJoins can result in funds going directly from a darknet market or entity straight to an exchange in a single transaction. At least with a mixer there is an intermediary in the chain which might give the exchange some breathing space, as it were.
Too many services have been freezing accounts for CoinJoin activity over the past year to say the distinction is trivial.
I didn't mean the distinction was trivial, simply that exchanges could equally as easily ban deposits from mixers as they could deposits from CoinJoins, if they chose to.