I will not consider exch as CEX or DEX either, its both of them, or probably a hybrid one that operates without KYC and don't hold user's funds.
There are only few decentralized exchanges. The two tht I know of are Bisq and Robosats. Also there was a wallet that icopress had free signature campaign for in the past that has an exchange, such can also be considered as a decentralized exchanges. I think its name is Peach Bitcoin. There are still many of them but those are the ones that I know.
Exch is an instant exchange but which people consider as a privacy means because they can make use of it with Tor and VPN unlike some instant exchanges that will seize users coins. Instant exchanges are centralized exchanges.