I don't know anything about video games, but I understand the piece is a heavily modified version of that tune... and yeah, part of the "charm" comes from the corruption of the way the software can't handle the extreme amount of notes. Like a weird digital and arrythmic version of amplifier distortion.
I guess I'm not surprised to see Touhou music being popular in this scene. It's pretty baroque and bombastic to being with, so taking baroque style to its logical conclusion is..... this. I'm not a fan, but I can see the thread. (Aside, if you want a modern take on classical music, check out some of the later Touhou soundtracks. You might find yourself surprised for video game music.)
Also a little Totaka's song easter egg in the middle of the first video, if you're into obscure video game minutia.