Chaosmancer
Legend
You're conflating two different things here. Oofta said high-stress rulings, where there's a real conflict with what a given player thinks should happen, are rare. Not that the DM making decisions or rulings is rare.
In D&D as usually played, the DM is constantly making routine adjudications. I share some of Scott's curiosity as to how this works in the described GM-less/GM-full game, which specifically says one of the player has the role of adjudicator/decision maker at any given time. Do they use a strict rotation schedule of some kind? Do they wind up defaulting to one player 80% of the time who's either charismatic, pushy, or just demonstrates a great creative flair and/or fair judgement?
While I agree with you that in most pure applications of the written rules where you're playing with folks who have good rapport, DM-as-authoritative-judge-to-lay-down-the-law is rarely needed, in instances where any kind of subjective judgment needs to apply, either you have one person saying "that's a great idea and I'm awarding a +2 bonus to your check!" and "yep, the tree is wide enough that you can hide completely behind it", or you have to spend table time hashing out all those little things amongst a committee.
Sure, but I don't see those as actually being that hard to implement.
"I think I'll jump behind this pillar and hide."
"Yep sounds good to me, in that case I'll..."
That's about all you would need, and they wouldn't really discuss it unless someone had an objection.