I'm not surprised with this development, centralized services will do anything to look trustworthy in the eyes of their customers but we know all they're doing is just marketing and don't actually care about their customers. Proof of reserve my foot, the only time I'll believe a centralized exchange has a proof of reserve is when their reserve/insurance fund are in Bitcoin and held in a multisign offline wallet which they'll sign a message including the Bitcoin address which can be verified by everyone and we monitor the address constantly.
I think you have a good point here because these centralized platforms can always provide fake proof of reserve. They can get funds from somewhere else into their business, conduct audits, and publish a healthy financial report. They will later pull out the funds they borrow to balance their account. An example is crypto.com which withdrew about 280,000 ($400m) from its account after publishing its PoR audit report. The funds was transfered to Gate.io's address fueling speculations that the funds was just borrowed to deceive their customers. Most of these firms show only assets without a comprehensive breakdown of their liability. So having a verifiable and constantly monitored wallet would be a good way to start. But even with this, they can still scam thier customers.