Another great channel is DotsAreCool. He explains how to manipulate the stack by placing turtle shells to skip to end credits.
It's pretty rare to have games where only the deeply technical memory glitch speed runs are a thing, much more often that's either a category few bother with or its forbidden.
It's more common in TAS because a TAS can manipulate things to a state where it's hilarious. e.g the increasingly deranged "correct" answers to TASbot brain age.
Video link: https://youtu.be/mSFHKAvTGNk
It's stupidly funny.
For example, here are the categories for SMW: https://www.speedrun.com/smw#0_Exit
A great example of the latter are the super monkey ball speedruns.