So, if It's glitchless, why do you do a gainer?

Because this is not a glitch lol

Well, I think it would be because the developer's don't intended for you to do that, but it is not really a glitch so ok. I am going to try and speedrun this game

We don't care about intention in glitchless. If we did, we wouldn't allow things like skipping half of Inverted Stone Tower Temple with a sidehop. Good luck on runs though!