But the latter is still not quite a "glitchless" run, based on the average person's definition of "glitch". For example, I doubt it was intended behavior for Kraid to die after 4 missiles [2] based on the player shooting him during a specific animation. I never played SM much beyond beating it as a kid, but I enjoy its speedruns because besides the variety of techniques and clutch moments required, there's at least one boss who behaves randomly, and requires the player to improvise. Also, in the course of new records being set, there have been a variety of strategies (e.g. different decisions on which path to take) employed, and there still seems to be room to discover more optimal strategies.
[0] https://wiki.supermetroid.run/Any%25_Glitched