You treated March as given. You did not say you were treating it as given. They staffed a contractor against March. March was a hope the model had turned into a clause. The contractor is now a sunk cost, and the conversation is about whether you "told" them the date.
That is the cost. Not a missing adverb. A plan built on a sentence nobody was invited to challenge.
The premise travels further than the message
Context does not transfer in the useful sense — the session stays with you — but an unmarked sentence transfers too well. It is copyable. It gets pasted into their board update. Their assistant pulls it and treats it as a constraint. A week later the guess is infrastructure.
Your AI has opinions. If you do not mark the opinion, their AI will not either. Two models, two confident grammars, one wrong date, and no label in the chain.
The people who pay are rarely the ones who wrote the clause. They are the ones who hired against it.
Labelling is cheaper than the argument
State the assumption so it can be corrected. One line, a source or the word "guess," specific enough to check. "I am assuming March because the last verbal yes was March; I have nothing in writing." That sentence is slightly embarrassing. The contractor is more embarrassing.
A labelled guess is a question. The other person can answer in a line. An unlabeled one is a brick. Removing a brick means taking the wall down. People delay that work, which is how a wrong date survives into a launch.
Approval is where the bill is assigned
If you confirm an unmarked premise, you signed it. The later claim "the model wrote that" is true and irrelevant. You were offered a preview. You let it go.
If they confirm a reply that repeats your unmarked date, they signed it too. The argument then has two owners and no origin. Labels exist so that argument never starts.
What the cost looks like in ordinary work
A vendor starts work you are about to cancel. A parent books travel against a weekend you only guessed. A counsel spends a day on a clause that sat on a hope. None of these people were in your session. All of them received a sentence that looked like a fact.
You cannot unsend the first briefing. You can send a correction that names the old premise and the new one, labelled. That is cheaper than a meeting called to "realign," which is the unlabeled assumption's favourite sequel.
Write the guess as a guess while it is still cheap. The cost does not stay in the draft. It shows up in other people's calendars.