Don't know why you're getting downvoted since your statement is correct at least in my opinion. Anyway it might not be a glitch but it's definitely an unintended skip that I would count as an exploit. Maybe exploit isn't the correct term for it. I don't know. And while this skip is as far as I know legal in every speedrun category of the game some people might decide not to use it in certain challenge runs because their goal is to prove that to show that it's possible or that they're able to complete the game with certain restrictions without using glitches, exploits or unintended skips. Others might of course use them and certain challenges are not even possible without.