It's this. Anyone who asks you a question and then interrupts your reply was either trying to ask a rhetorical question (which is ambiguous for anyone in this scenario, neurodivergent or typical), or is acting in bad faith. You're completely justified in feeling frustrated by it.
That question can be clear by tone, and by level of trust.
I'm a very curious person, so I want to understand what drove a decision (even if it was "I don't know" or "Just seemed like the right answer"), and I want to understand someone's approach to things - there's lots to be learned that way.
But yea, quite often it's a rhetorical, judgmental question.