It's also misunderstanding the question, either due to being stuck in thought of due to ambient noise. Absent-mindedly understanding the question as "is this the train?" or something would not surprise me.

A lot of people are also too afraid to say they don't understand or hear you, and will just go "yeah yeah". It's aggravating, but it's both real and no real ill intent behind it.

It’s not much a lie, it’s more of a way to quickly get someone to sod off. Still a shitty move.