This is beyond my level of understanding. If this is true, my question would be why was whirlpool so popular if it was really that easy to unscramble? I think they had over 10k bitcoin moving around before the arrests. And also if it were true, why didn't someone show us just ONE example of where their conjoined UTXO's went. Just to prove it didn't work and stop people from using it.
The labeling attack could be done by the coordinator, i.e. the samourai guys. This means that if they were bad actors they could decrypt the coinjoins, it also means that even if they were not bad actors if the coordinator was taken over by some 3 letter agency (knowingly or unknowingly) they could perform the attack themselves and it also means as has happened that if an agency seizes the coordinator's server and they have not deleted the logs it can also be decrypted. So it is all a matter of faith. Other coordinators and coinjoin methods have this problem mitigated.