I don't think calling a web3 casinos as a decentralized casinos is true to its core. They're more like a semi-anonymous casino, where player does not need to provide ID and can conveniently connect through wallets.

However, much like you said, some elements are still centralized. They still pool funds [and I assume they have full control of this pool] to take from loses and pay the winnings, and they still collect sensitive data like device fingerprints and IPs to identify abusers, of which the data [I am somewhat sure] are stored centralizedly.