You are still lucky that Duelbits will just ask you only KYC to withdraw your funds because if you are using mediocre casino and committed this same violation to there ToS. There's a high chance that they will freeze your asset and ask you too complicated documents that will let you give up on claiming your funds.
Undergo the KYC or leave it there is your only choice since you are responsible to your action due to Duelbits didn't forgot to remind you about this on there ToS when you click agree during the registration process.
He already answered his own question there. The site ask him a kyc which means there is a chance that he can get his money but if the site will deny it, they already have done it earlier but they should state the reason for it so that players will know just in case they are wondering why does it happen. Each casino has its own rules. Some are strict and some are not.
It must be the old/famous casinos like duelbits are the ones that are strict and not the newer/unfamous ones because they are still on the phase of attracting customers but I salute duelbits there for not totally confiscating the funds of this user. One must not give up but will provide any documents being asked, no matter hard it was if the money that are in stake is too huge.