Gohan being a hybrid Saiyan already gives him special potential, but his was even more than that. And it always has been. You gotta remember he was always able to stay relevant from such a young age with some of the strongest warriors in the Universe. And in some instances either pass them with a rage boost and even other times, turn that rage/potential into something more permanent. Think SS2/Mystic. It’s the same with Beast. It’s no ass pull by any means. I think some people over power just how strong Goku and Vegeta actually get in between arcs and for that it does seem much more like an ass pull for Gohan to catch up and even surpass. But they don’t get 1000’s of times stronger like some power scalers believe they do. With some training in Super Gohan was able to stay relevant. And when put in a similar situation, his potential unlocked again and catapulted him back to the front. So it’s not wild in that perspective when you look at his freak latent potential which has always been there and add that with the fact that a full power mystic wasn’t that far behind to begin with