The problem is not in "kycfree" or "only-Tor", with a 99% probability the thread was moved to the archive because the interface allows you to exchange "BTC for BTC".
I use the onion site again and wanted to use it to exchange bitcoin for bitcoin and I saw that you are right. The site would be said to be a mixer because of that. An exchange should be a platform that one coin can be exchanged to another and not the same coin. If it is the same coin it is a mixer.