But I'm also 100% sure that they will go thru the KYC and AML checks for the customers.
From what I know, if the account is on the same name (i.e. yours) on Revolut and Bitstamp, you can withdraw fiat from selling crypto. I don't know though whether there are any limitations.
And while Revolut is not a bank, indeed, they use banks' services and offer account number, maybe numbers - which may be even from different banks, one for EUR and one for local currency.