There's an infamous bug in Version 1.0 of the game where you can set a stop at the computer's untap phase, and you can tap their lands for mana, causing mana burn and prevents using those lands.

Does the speedrun make use of this?

No, the speedrun doesn't take advantage of that. Honestly, I feel like it'd actually be slower than what the speedrun actually does which is get a shivan dragon and rush the 5 castles.