"Reading their resume" means not giving me more info beyond what's literally in their resume.

Example: "Oh well I've worked with React before. It was an interesting project. It was for an ecommerce project. (endless silence after)"

"Start saying nonsense" means they're just making things up.

Example: "So yeah I've used git before. It's a cool programming language. It reminds me of C. I love programming."

I’m always mildly confused by the question. Makes me wonder if you read my resume.

Still, I ask the question in more or less the same way during interviews. How people respond is more interesting than what they respond with.

If you're interviewing with me I definitely read the resume. Not all places are the same though.

Occasional mild confusion in a good candidate is worth stumping the bad ones often. I do feel slightly bad, and I admit it's slightly rude, but it works and the interview process is what it is.

By the end of the interview, the rough start is hopefully forgotten. If you ever get this question upfront again hopefully you understand why and roll with it.