I'll move this discussion here because I don't want to derail the Unijoin thread by talking about the Sinbad mixer
They could blacklist any address they want and sending anything from that address to exchange would trigger automatic alert on their system, that could freeze your account.
I think Unijoin is smarter with addresses than other banned mixer you mentioned and they wont get connected with notorious hackers group.
They could, but they didn't. My conclusion is
Sinbad signature escrow address -> regular wallet -> Binance / there are no, or there were no additional checks
Sinbad signature escrow address -> Binance / Binance requested additional checks on the owner and origin of the coin
Looking at the whole thing about Sinbad, didn't they turn out to be quite wise, because all that was found with them was the escrow address (publicly posted) from the signature campaign on Bitcointalk? Around $13k at that moment, filled a few days before.
Remember Chipmixer, who had a huge amount of Bitcoins, servers, and data seized...