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.
Yeah, I read that user's sad experience with Bybit and I understood why Bybit would be that harsh with the conditions it asked the user to meet. However, it goes to show that even the mixers some of us thought protected our privacy (for those who use it, anyway) may have done us more harm than good.
So what we learn is that funds shouldn't be deposited to a centralised exchange directly from any third party. You should bring the funds into your non-custodial wallet first. Then you should use CEX to buy crypto coins and move them again to a non-custodial wallet. In the meantime, if the exchange is about the source of funds, you can show them with video proof, etc.
You meant after sending the mixed coin to a non-custodial wallet, we still have to wait and then buy from Cex and send to the same non–custodial wallet to neutralize whatever effect a mixer might have had? If that was your case, let me ask – what if the person doing all this doesn't have extra bucks to get coins on Cex?