And we have hundreds of stories from these no KYC exchanges that suddenly decide your funds are suspicious and ask you for every single possible document, knowing all to well you will not be able to provide them and just freeze your coins. To whom are you going to complain? File a report against a company in Cayman Island or Bahamas? 
Literally any mixer could freeze any order for whatever reason known to man. And it's not like this hasn't happened before.
From admins going AWOL to simply not caring to maintain their systems, all the way to outright scams. Mixers are also a 100% centralized and trust based system. There's not any documentation proving that they're better at what they claim to do than a simple exchange.