If so, then you can not say that Monero and fiat are separate.

?? Example Haveno: Ali from Istanbul sends Bob in Berlin 1000,- Eur. Only Ali and Bob know what the 1000.- euros are for.

I am thinking about some KYC on a XMR buyer side along with some way XMR seller leave a review on a buyer in case trouble with fiat. The DEX I am unsure if supports KYC+feedback.

The main point of Bisq & Haveno is NON KYC! “in case of trouble” That’s what security deposit is for. It is punished with XMR. For this reason, very little fraud has occurred in the last 8 years.

Somehow you contradict yourself. You want untraceable transactions first and then KYC.

Every dollar in the world has been used by criminals to purchase weapons or drugs. Often even supported by governments. Cocaine can be detected on almost every euro note. Fiat is fungible & Monero is fungible. So who cares?