Notably, the speed at which particular block chains break (Seen in Room 5 of The Lake among other places) is so glitched that only a single block breaks, creating a softlock this requires one to exit the game and re-enter to choose a proper difficulty to proceed.
It is possible to skip the difficulty selection at the beginning and save about a second, but this brings the game into a glitched difficulty state. The only thing that slows Intense down in comparison to lower difficulties is the fact that bosses have more health and characters take slightly less knockback, but they go down so quickly that it hardly matters.
Factors like enemy damage and autoscroller speed increase as difficulty increases, making Intense Difficulty actually faster than easier difficulties in most parts of a TAS.
