I don't know when did this new updates took place because the last time I checked, banks were warning customers not to use accounts for anything crypto related to avoid freeze of account. Maybe, these banks just wrote it and haven't started operating on cryptocurrency. I will advise you not to use your bank account to buy crypto directly but use p2p trade to avoid trouble.
I am not doubting you or saying that you are wrong about the statement on banks warning their customers against crypto related dealing but I have a question.
Have you checked out how active Crypto-currency exchanges are in Nigeria, I refuse to mention some name. And do you know that their are huge peer2peer transactions going down on that exchange? And peer to peer involves the buyer send naira to the sellers account. This has been the situation.
We should know by now that the government can not stop crypto-currency no matter how hard they try.