Gambling needs to be well categorized. There are some that are skilled based and doesn't really qualify as gambling or game of chance. For example, what do you call two gamers (with one better than the other) betting on outcome of their game? I guess the outcome can be fairly predicted hence not qualify as game of chance.
That is also gambling. You are betting on the person who will win and there is a 50-50 chance regardless of the level of players or the skill involved by them. Its basically likes sports betting where one underdog faces the overlord. There will be a chance to maximize profits by betting on the underdog but they will rarely win here. Even then the pure chance is always 50-50 for both.
Your analysis is correct and you may profit from that but does that matter to the mathematical outcome of a completely random event? It does not. Secondary is that fact that the underdog will lose 90% of the time.