In the more recent times quite a bunch of the PlusToken scam coins have been dumped on Huobi and a chunk on OKEx, and that not once, but multiple times. How come these exchanges don't freeze their funds? They probably are making a killing allowing these scammers to dump on their exchange stealing liquidity from the ecosystem.
Both exchanges have KYC policies in place, so they know exactly who does what with these coins. I wouldn't recommend anyone to use these exchanges. Steer clear of them!
Huobi may mandate KYC but it's moot since the PlusToken scammers used OTC brokers as intermediaries. They also used mixing/coinjoins and generally employed a high level of effort at obfuscation prior to dumping the coins.
For the sake of Bitcoin's fungibility, it's probably for the best that the funds weren't frozen.