They believed that if a gambler wins a jackpot, he or she have won the casino, could that be true?
It's no brainer, and that definitely makes him a winner against the casino. Unless that jackpot winner goes back and lets it lose again to the casino.
Some people can win a huge amount as jackpota but yet the amount that they won can not be compared to how much money they have lost in entire life while gambling, can you say such person has won the casino because they won a jackpot?
If you believe that sometimes, gamblers can also win the casino, kindly drop all the explanation of why you have such a believe.
Even if that's the case, if they tell themselves and proclaim it that they're winners. I will not cut the fun that they're having and experiencing at that moment. I'm no killjoy and will just allow them to enjoy that winning moment even if they're still not breakeven with their losses.