So yesterday, I made a huge discovery: In MAP30, The Lair, there's a set of dummy sectors just outside the starting area, and inside one of them, there's a usable line that when used, directly takes you to the end of the game. Miraculously, you're able to use this line even without any assistance from lag clips, so it's now possible to beat the game much earlier by using this line in this level.
https://www.youtube.com/watch?v=34--yKSmEyQ
For now, I won't be making another TAS that uses this until better emulation is a thing. When/if that eventually does happen, I'm thinking of treating this exit as a separate category since it cuts out a large portion of the game that you otherwise wouldn't be able to see. This isn't exactly a game end glitch either, as while it is unintended to beat the game this way, the fact that the game ends is a result of intended game mechanics and not memory manipulation.
A brief explanation of what is happening: This game handles secret exits differently than Doom 1 or 2. Instead of the secret exit taking you to MAP31 by default, they made it so that the secret exit trigger will take you to the number of the map of which the line is tagged. For example, a secret exit line that has a tag of 28 will take you to MAP28. If the tag doesn't correspond to a level that exists in the game, however, it takes you to the ending sequence. In this case, the secret exit line has a tag of 70. Since MAP70 doesn't exist, it takes you to the end of the game instead. This is exactly how the game takes you to the end after The Absolution, which is why I know this is the result of intended game mechanics.