This looks trap, if casinos do that trick, better to avoid them and to do not register and play even 1 cent. I don't know why they bypass it on the beginning, if the user breaks the rules of VPN, it's better to ban him at the beginning before continuing to make any big winnings. I still don't know the rules of DNS, because I never heard the specific rule about that.
It's not a trap, even a trustworthy casino can did that. This because it's up to them when to accuse the player, there's no written rule if the casino will ask the user KYC if they're using VPN usage. Not to mention there's few casino ask user KYC when they want to withdraw their winnings.
DNS will mask your real IP address which is still similar like VPN, it's work different but you're still break the TOS of the casino, avoid to use it.