Basically we've engineered it so that the players and their characters get on the same page very quickly. If Falstaffe's player puts forward the idea to go after the evil wizard, Grog's and Halfred's players will figure out a way to get Grog and Halfred to go along with that in a way that makes sense for the characters. Next time, Falstaffe will defer to Grog or Halfred instead.
Yeah, if this 'agreement' was a DM-enforced thing that would certainly count in my books as a DM flaw, under 'severe violation of player agency', that would cause me to leave a game.
As for spending an entire session on player or character debates, I'll take a hard pass on that. The second I hear a "Yeah, but..." my blood pressure goes up because I know we're headed toward a time-wasting debate.
That's because you're too worried about getting everything done right now. If a long in-character debate is looming then pour yourself a beer, sit back, and take it easy for a while. You've always got next session, or next month, or next year....the campaign you're running is designed to last the rest of your life, isn't it? If not, why not?
The table rule is that if you can state something as an action, do so. Don't try to hide an action in a question to force the DM to assume what you're doing and potentially avoid consequences. If you legitimately did not hear the DM or don't understand a word or something, then ask. But otherwise, have your character do stuff to get the information you seek. This keeps things moving forward.
This is fine.
Otherwise we're stopping the game for you to have a little side-chat with the DM and that's not going to work for us.
But how do you get from the last bit to this in one leap? Just because I'm the player asking the questions doesn't mean I'm the only player who wants the information, it means only that I'm the one who happened to ask. Also, an action can quite often be stated more succinctly as a question and-or simply contained within it. Example:
DM: "...and at the edge of your light is what might be a stone altar - it's hard to tell but there could be wispy smoke rising from its centre."
Player: "Can I see a source for the smoke - something burning, maybe - or is the smoke coming from solid stone?"
Here the player skips the words "I look more closely at the altar from where I'm standing" and just gets right to the point; and I don't mind this. If I-as-DM am uncertain whether the character is standing pat or moving closer, I'll just ask. And even though it's just one player asking, the whole table is likely interested in the answer.
However much some want to justify gotchas as being a thing that could really happen, they are still unfair game play in my view and tend to lead to players being overly cautious in a way that impacts game pacing. Telegraphing and the certain knowledge that the DM isn't trying to hit them with screwjobs all the time sorts that right out. If your character takes a beating, you can be sure in my games that you were fairly warned.
Again with the pacing - this seems to be a theme of yours.
It's quite realistic to posit that sometimes a character is going to take a beating simply due to sheer bad luck, and other times due to its own (via the player) misjudgement, and other times because it simply couldn't see or know what was coming. It's war, not sport.

By the same token, it's reasonable to assume the characters are taking some precautions, and if the players want to detail these it's well worth the time spent.
DMs in my experience seem to have a problem separating a basic NPC interaction for color with an actual social interaction challenge. So everything's a challenge of one sort or another for no good reason and, often, it's just really annoying. You'll know if you're in a bonafide social interaction challenge in my games at which point you'll know you're trying to accomplish something important. (I've written a bit about how to structure these in other threads.)
To me this needlessly provides information to the players that the characters wouldn't have, leading to some metagame headaches that could very easily have been avoided.
They talk to three shopkeepers. One of those shopkeepers is a spy for the enemy. Telegraphing that there's a spy out there somewhere is fine in some situations but not in others; placing undue emphasis on the PCs' interaction with the spy over the other two is always wrong IMO, as you're in effect leading the players (and by metagame extension, the PCs) along what amounts to a soft railroad. Put another way, emphasizing that one interaction is - though slightly more subtle - roughly equivalent to putting a sign over that shop's door sayng "THE SPY IS IN HERE!" and narrating that.
One shopkeeper could be a jolly old lady willing to chat about nothing all day if you let her.
One shopkeeper could be a sleazy guy familiar with every shady sales technique ever invented.
One shopkeeper could be a no-nonsense military veteran whose fighting days are over.
Which one's the spy, if any? By what you're saying it would be the sleazy sales guy every time, and so much for that mystery. Were it me that guy might be a potentially-time-consuming red herring, as would the talkative lady: the ex-military guy has gone rogue against his old bosses and is now a secret agent.
And if the PCs take all session and half the next trying to figure this out, so what? And if they never figure it out or completely ignore it, too bad for them. But if they do figure it out they have an advantage - they can try to charm or turn the spy, or they can feed him false info, or they can report him to the militia...all kinds of fun can be had.
Lan-"secret agent man"-efan