Yeah, a clearer explanation in the rejection email would have been nice, or perhaps even a warning in response to the proposal (though it's not 100% clear from the proposal alone that OP would be going down a path that ignores that part of the assignment.) But the prompt explicitly lists other terminal clients as the inspiration.

Also, the prompt for a terminal client really changes what they're testing! Email web UIs have been a known quantity for years. But the UX of a terminal client is still something that's not "solved." I suspect the rubric for the question has large sections about how they decide to make a terminal client that OP's submission doesn't address at all