Yaarel
🇮🇱 🇺🇦 He-Mage
I would say a question is typically a goal without an approach - the "how" is missing. Okay, your goal is to see if the guard believes you. How? I can't determine what happens next unless I know. It might mean auto-success, auto-failure, or a check. And their approach to the goal is going to allow me to set a DC to resolve the task, if it's uncertain. So I need this information. The players have ONE thing to do in the basic conversation of the game: describe what they want to do (Basic Rules, page 3). Let's ask them to do it!
Consider also what a great advantage it can be to ask questions instead of take actions: You can fail at actions and sometimes that has consequences. Questions are far safer! (Super common.) There's really no reason why it's so common a way to play in my view.
Anyway, this is getting pretty far off-topic so I'll try to bring it back around: So far as I can tell, how one thinks about auto-success with regard to the adjudication process can be a way to address at least one of the objections to Expertise.
So. A player wants to know if the guard believes what he said.
What should this player say or do for you, to satisfy your needs to determine an adjudication?