What does it mean for an interview question to be contrived?

So overly specific that it feels inappropriately artificial within the context of testing a stranger.

Yeah, the kind of question that I'm not comfortable giving a vague nonanswer to because I'm not familiar with all the intricacies they spent months ironing out. Which then turns into "what do you want me to say" whackamole of endless questions to gain the context needed to actually answer their question. Usually asked by people who cannot provide the context that actually led to the answer but still believe they understand why it was chosen.

It's a pretty specific scenario but it's happened to me

If the question is sufficiently related to the actual application, it could be an interview of the "solve our biggest problems for us, unpaid, without context" form, which I experienced once at a tiny startup. The technical lead just sat there silently as I probed with more questions. Eventually, I set down a boundary and let them know that that is something for the business to solve.

Maybe contrived wasn’t the best word, but I’ve been asked to implement a simplified feature of the company’s product. So at one company I was asked to create a simplified model for their product with support for undo/redo.

This is my favorite, “we want you to work for free”

No they definitely aren't using my code in any way. During the interview they are trying to see how I approach building something they have already completed.