I guess we'll have to agree to disagree then. If customers didn't want their USDC deposits converted, they shouldn't have used Binance. Its not a public service company. Same goes for your expectations of custody, they never claimed to be one.

Conversions are even announced when you go to deposit USDC:

"Please note that your USDC Deposit will be auto-converted to BUSD at a 1:1 Ratio. Please refer to announcement details. https://www.binance.com/en/support/announcement/e62f703604a9..."

I don't see how your point holds, besides "customer expected X, but got Y" - but this is because customer is misinformed, not because Binance has an obligation to store USDC 1:1 (in this case).