So even the providers of these services cooperate with the authorities and payments may not be processed if they are on the OFAC list, yet they are mixing services.
Yeap, I guess that probably that was mentioned in
FIOD article under the point about KYT policy:
In the case of Sinbad.io, more than 50 percent of all mixed cryptocurrencies were found to have a criminal origin. In the case of Sinbad. io, there are no measures in place to implement and enforce a Know Your Customer (KYC) or Know Your Transaction (KYT) policy.
Of course we don't support criminal activity in Bitcoin or crypto, but according to the Chainalysis data
just 0.12-0.24% of Bitcoin transactions is probably related with crime; and as for Bitcoin mixing, then
more than 90% mixing is made by law-abiding people. So if mixers don't let to use their service for those who stole money by hacking different projects etc, most of mixer users will even not find that out ever.