Base on your detail explanation, other cryptocurrency exchanges are not decentralized exchange platform? If they are not, then why do they classify themselves as being a decentralized platform?
The confusing part for ppl is the "EX" of "DEX". i.e., what constitutes an "exchange". All are non-custodial. (The "D" is not without its controversy as well...as in the degree of decentralisation to qualify for being a DEX). So there is a broad spectrum of what constitutes a DEX. Like LEVERJ is going to be a hybrid DEX, non-custodial, but with centralized order book and matching (secured by fraud proofs).
https://blog.leverj.io/gluon-plasma-security-9d422180ade9