Thanks for sharing that note btw.

Sounds like this guy sent coin joined UTXOs on-chain to Strike. I believe the same outcome would happen on any US based exchange. I do not think this is Strike specific.

I believe they could have avoided this by using your cleaning method and send sats over lighting vs. onchain but honestly this use case is not great. I would never recommend anyone use any KYC service this way.

Spend bitcoin using sovereign wallets/tools. If you must convert to fiat there are other ways.