Lanefan
Victoria Rules
If the character is impatient and you-as-player want to play it as impatient, don't tell me up-front you're waiting for an hour. Tell me up-front you're waiting for 15 minutes, or however long you think your character can last without doing something rash.So people in your world cannot change their mind mid-task? Hunches only come up at pre-determined times?
Because yes, once you declare your action you're committed to seeing it through barring external interruption. For example, in the scout situation I might get the party to tell me how long they're waiting (let's say an hour) then go and play out the scouting. Let's say the scouting goes well and the scout would return in 45 minutes. Before the scout's player comes back, I return to the main group and see if anything has interrupted their waiting. Look, a wandering monster or patrol came by at the half-hour point, what would you do? And I play that out. Now that I know what happened there, I can go back to the scout player and tell her what she sees on returning to the party.
"Disperse, don't group up!" implies knowledge of how the breath weapon works; knowledge the PCs may or may not have. "Don't stand in front of it!" implies knowledge that it likely has a breath weapon of some sort, which is common knowledge even among peasants thanks to far too many Bards telling stories for coppers.Why is breath weapon "fairly common knowledge"? Has that been decided in some way ahead of time? Has it already been established?
This is my point... why require that players pretend to not know what they know when it comes to this stuff? It actively highlights the metagame aspect rather than avoiding it.
If someone in my game said "Disperse, don't group up!" I'd assume they'd heard about a dragon's breath weapon, or otherwise intuited the risk, and we'd move on without any disruption at all.

Ah, but yes it would. That player would have knowledge of them that the character would not, and be caught in the trap of either metagaming to use that knowledge or metagaming to not use it. Either way, the purity of in-character decision-making would be reduced.And nothing would have been different if one of the players was familiar with arakocra.