Firstly, we are not all US-based, thus, we have different taxation laws regarding crypto. Secondly, we are talking about coins, their prices aren't stable and this alone changes things regarding tax. I mean that all the cases aren't the same and prices can affect a lot. And thirdly, why should you do it from a CEX? Regulation doesn't necessarily mean safety. There are non-KYC ways trusted enough for using them without issue.
Replying in no real order.
Not saying the OP was legit unless someone here comes out and says they did the deal we will never know.
It's not just the US a lot of places are no longer playing "fast and loose" with the rules in terms of things. Yes, there are a lot of countries that don't care, but those numbers are shrinking. So, more and more at least in my opinion, we are going to see people more interested in F2F things like this.
There are many non CEX ways to do it as you said. But if you do not know them there is time involved in finding out which one would work for what you need. And time=money and if you pick the wrong one it can get real bad real quick.
EURC is a stablecoin so if the OP really had $11000 of it there is (in theory) no fluctuation. The amount of
BTC you get back will vary based on price but he was asking for $10k worth of
BTC in return for $11K worth of
BTC when he pays it back. You could in theory have sent him 0.11
BTC and if it keeps climbing only get 0.1 back. No different then when people ask for a 0.05
BTC loan and offer 0.055
BTC back. If
BTC drops more then 10% and you didn't have an agreement about that beforehand you would have to wait for
BTC to go up in value to actually make a profit if you need "real world fiat"
Also, as a real world example a few years ago I sent a friend in Spain a significant about of crypto that he sold for fiat. Now, he just wants me to send him stablecoins since it's easy to show value in and out.
-Dave