Are you sure that fortunejack will ask for KYC?
Based on my knowledge they never ask you any KYC but if you win big amount then they will hold your withdrawals until they verify all the bets to make sure nothing went wrong. If all okay then they will release your funds but I never heard that they will ask you any documents.
It's for security reason since it was talking about huge amount ,
But AFAIK there's no case both fortunejack and primedice ask for that kind security measure ,
Both reputable , but it seems each gambling site will always have different plus and minus. Depends on your taste.