It’s interesting to look at gambling as a kind of mind sport, but we shouldn’t mix things up. Chess or professional poker really develop strategic thinking, attention to details, and the ability to predict an opponent’s moves.
As for blackjack or sports betting, I believe they challenge a different set of skills and require a combination of discipline, experience, and quick decision-making under pressure.
It's all training in some sense, but it also comes with risks.
It exercises, trains and stretches the mind, right? Then it is a form of sports. Every challenge that involves some mental skills has a way of developing the cognitive rating of the mind, it makes it sharper, more attentive to details and having a higher degree of accurate decision making. These skill-based games does the magic, especially when you are consistent in it, overtime you tend to build professionalism on them and the more you get better in them, the more critically you tend to reason and the better you get at decision making which validates your excellence in those games.