I wouldn't say that is a glitch, 9.1 was an unofficial modification of the original arcade. Some of these mods let you get to the secret characters faster.
I really wish Liu Kang's red dragon and Kung Lao's bones in a hat fatalities would become known, if they even exist. They're said to be in 4.2, so they should be in 9.1 as well.
So you're the YourMKArcadeResource guy on YouTube? If so, I'm a fan of your videos. Good stuff.