An answer is more useful when its limits are stated plainly.

An answer with no stated edges gets used well past where it holds. The person receiving it has no way to know whether you are certain, guessing from one case, or repeating what you were told, so they apply it with the confidence they heard in your voice. Saying where your knowledge stops does not weaken the answer; it tells them which parts they can lean on.

Add one sentence about the boundary: this is true for the standard case, I have only seen it once, check before spending money on it. When you receive an answer, ask what it does not cover before you act on it.