I don't think that example is actually a good one. Exchanges need at least 2 people in order to do trades, whereas this particular case we've been discussing (which now brings up the question of whether this should be continued in gambling discussion) only involves one person.
It only involves one person if one person is playing against himself, in the Casino, as far as I know, you are either playing against other gamblers or the dealer of the Casino, if you are playing against other people and the Casino is only collecting fees, then the Casino is responsible for guaranteeing payment to those who win. So if someone loses and double-spend that money, the Casino will have to cover that loss.
In the event of playing directly against the dealer, the Casino is actually the other person, the dealer is counting on the odds which favor them by a small percentage which depends on the exact game.
If 100 people play an online game on which the Casino has an edge of 1%, each with 1 BTC, on average 50.5 people will lose, 49.5 will win, the Casino will make 1
BTC, if a single person double-spends a losing game the odds shift against the Casino and they are guaranteed a loss, the loss will be in their trial balance, no matter how you look at it, it is a direct loss.
I still see making a double spending and not doing a deposit as the exact same thing
Only if the person did not play any games using that double-spent amount, the moment they do, they have already created an impact on the win/loss ratio of the Casino.