The point is that the numbers don't add up.
If Consumables + World buffs double your dps, you aren't taking any breaks for mana and just chug mana pots / runes instead, you're not just going 20min faster than a random assortment of 30(!) people, especially if you are 40 on top of that.
In your average MC pug, especially in one without voice, it's more likely that someone body pulls some trash mob, which can be threatening depending on your situation, because some trash mobs in MC just straight up kill people and ressing (multiple) people in Classic eats up time. a lot.
In order to do such a quick run, you need to skip mobs that can absolutely be bodypulled.
Considering those are used for speedruns, that's irrelevant.