It's not entirely about whether or not Ash himself has learned how to deal with losses, but how they play that factor in the anime. If they wanted to showcase him having surpassed that, then why even have the depression arc in the first place? Have him bounce off from the defeat by himself and then beat Bea in a rematch rather than having to go through something so redundant, wouldn't that be right? The point made here is not that Ash should or shouldn't have sad moments after losses, but rather how the show wants us to believe that he would throw a tantrum and do nothing about it until someone force him off from it, which in Bea's case was Goh, when he should have had already been over that when it happened multiple times in the past, the Kanto and Bea comparison was more about how in one Ash was properly disappointed with his performance, and then swore to better himself in one of the most iconic scenes in the anime, while in the other he DID throw a tantrum over something little that he should have expected to happen eventually, rather than properly take the L.Pretty good battle
Ash literally did not care he lost the Kalos League which was the most important match of his life at that point. It’s been like 25 years since Kanto and 90 percent of his losses he learns to take in stride, he’s not gonna throw a tantrum every single time.