I will share my own experience. Binance freezes my funds when I receive funds from my clients. Because one of my clients sent BNB from a mixer. However, eventually Binance returned my funds but restricted my account, so I can't use Binance anymore.
This seems so strange to me because I have not heard that CEX forbids deposits from mixers. I have used CEX to receive funds from various third parties and there have never been any issues so this case is a kind of strange to me.
The second story was learnt from the scam accusations board. Bybit asking him for transaction details with videos of where he got the funds. That user also used a mixer to send funds to Bybit 5 years ago. So Bybit is asking for proof source of funds, which is impossible.
This one is an unfortunate situation because even if the funds were sent from the user personal wallet, that does not proof the source of funds assuming he received them from a mixer before sending to Bybit. I think that case is just CEX being funny after confirming the funds came from a mixer.
What I seem to have gotten from the whole story is that centralized exchanges are gradually cracking down of mixers or trying to use mixers to punish their users.