I would absolutely NOT ever give my bank statement out to an online casino, that is absolutely asinine. You’re write up here is a bit confusing as well. I’m assuming you sent money via your bank? This is where bitcoin has become such a big thing for online casinos. I understand there’s still often know your customer rules and verification mandates, but never ever would I do so by using a bank statement.
I agree with this. You are entitled to your privacy. If they want to verify your account and wants to make sure you are really the owner of it, they can ask for KYC using identification cards, utility bills (for residential proof), and facial recognition to verify if you are really the one signing up for the account. However, sending a bank statement for verification is a little bit too much. This is a common protocol though if you want to open a bank account and to receive a debit/credit card, but it is unusual for a casino to ask since they don't need to see what's in your bank statement in the first place.
But oh well, if ever you find it sketchy, just don't push through with it. It's still better to be safe than sorry afterwards.