“Paper” Coins On CEXs and ETFs

I’m just curious if anyone can provide some information about what assurances we have that CEXs and ETFs are actually buying coins for the custodial wallets. The reason I ask is looking at the XMR chart it has been rising when all expectations should be the opposite. It’s difficult to buy, has bad press etc. However a main theory on why it’s increasing is that there is no more paper monero. Since it can really only be bought P2P, we are seeing supply tighten as all the paper monero is flushed out of the system with delisting.

It seems to be a convincing argument to me and if this is an example of catching CEXs with their pants down, how do we know they aren’t doing it with other coins.