the forum has no choice in the matter
what you dont realise is this forum is a service in the US jurisdiction meaning US law
when there are regulations involved. these cannot be ignored. as it can involve court orders, and if ignored.. court dates, fines, prison for not complying
what i believe to have happened is the Mixer owners that purposefully and in full knowledge processed sanctioned/illicit funds for a fee and got caught and charged, triggered regulators to want to gather any and all evidence about that charged suspects activities, and with them having a account on this forum promoting mixers, the task force then requested any and all information on this forum about that account holders activity..
(well thats what logic and common sense would suggest as natural chain of events of a mixer operator being caught and charged for facilitating illegal funds)
secondary to this any private or public communications or commissioned promotions with other users would then trigger those other users details to need to be investigated and collected too.. and so on
so to avoid all these legal orders requesting data on users.. its simple and much better to not advertise things that have legal ramifications