>>15456028
What this anon said is correct: >>15456063
Allow me to explain in a bit more detail for anyone curious though.
In the game's memory there is a value that corresponds to Mario's vertical speed, this specific value relates to Mario's "falling" state which is active whenever you're in the air (this changes the physics acting on Mario so that he gains negative VS when in the air constantly, while not gaining any on the ground since eventually this would cause him to fall through the surface he was standing on) obviously this value is updated when you jump, fall, get lava boosted, and so on, but it is also updated when you do many other things, walking on the ground happens to be one of them. Specifically, taking a step sets this value to zero, this is intended to be a sanity check of sorts, obviously if Mario is walking he is "grounded", he is not in the air, not "falling", and he shouldn't have vertical speed. Moving up slopes works differently before you ask, it doesn't change this value
By landing the way he did he stored the vertical speed granted by the lava, then used punches (which as stated by the previous anon, do not update the VS value) to navigate to the other side of the platform once it had risen high enough. When he punched and fell off the edge (transitioning into a "falling" state) the game began using and updating his VS value again, resulting in that "jump" that you saw.
>>15456150
>I don't know how to categorize it correctly
This is really the problem with the idea of banning glitches because they don't make a "proper speedrun", there is usually no way to categorize it properly. To be more specific, what constitutes a glitch that is "too massive" is very subjective and as a result each individual person has a totally different set of rules they think should govern the run (which invalidates the concept if you can't agree on a set of rules, and prevents you from comparing your times to anything except your own runs). If there is a way to classify it easily, a category will usually pop up with the direct description in the ruleset of "complete the game without [major glitch] being used" and create exactly the type of thing you're talking about, this is why "glitchless" or "no major glitches", "no out of bounds" etc. runs exist at all though one of the biggest problems with those runs is that the list of banned techniques is always entirely arbitrary and subjective, frequently invalidating runs because of rule changes and leading to people crying about glitchless using a "glitch" because they take advantage of grabbing a ledge the developers didn't think you could to so they can skip a puzzle or something