So it's normal in my opinion. It's not againts and I also think that I don't see anything wrong with something like this. Toss has a gambling casino. It's only us gamblers who probably give it a bad meaning, after all we are not forced to play on their platform casino.
It's really normal for a casino to change ToS without any notice to players but the main point of discussion here is the change of ToS just to use it against the existing case of user. It's not ethical to change ToS just to have an advantage over the players since it's like bullying players without a chance to explain. The good news is, Only shady casino do this kind of trick while the rest of the reputable casino don't modify their ToS for the purpose of taking advantage on someone case or to prevent someone to withdraw profit.