No he doesn't regress. He has the same maturity as the last season he was in. Currently he is as mature as he was in Sinnoh. Which is more mature than when he started in Kanto. A lot of his tactics is his personal views on battles. He likes to challenge himself so he purposefully chooses match ups that are bad for him.
He even taught a child how to use his Pokemon so the kid could have a Pokemon battle with his friends in one episode. He has made a huge leap forward since beginning and is a completely different trainer than when he first started. He just likes to take unnecessary risks in battle just to see what would happen.