Exactly: if they just buy and sell through a decentralized exchange, there is no definition or check for taint and thus also no 'risk of taint'. This is only introduced when you start using services such as centralized exchanges and Wasabi.

I don't understand why people are so hellbent to play by the arbitrary, subjective 'taint rules' that a small group of companies are trying to put on Bitcoin to make more money from large investors. Like, you get 0 benefits from using these companies as a customer, besides maybe 'convenience' (mobile app etc), though I don't personally consider an exchange convenient that charges between $5 and $20 to withdraw Bitcoin, that requires me to go through KYC to register there and that can close my account at any time.
I consider Bisq much more convenient: download and verification takes just a few minutes and you're immediately up and running, ready to get some coins. No questions asked, no paperwork, and withdrawing costs only as much as you're willing to pay for transaction fees and how full the mempool is.

But I will now stop arguing with Wind_FURY since we're already repeating ourselves and if he doesn't understand after 2 explanations, 10 won't help either. I don't feel like adding any value to the forum by repeating myself over and over.