If I’m responsible for it then I should have some experience with it and understand the code already. I can call upon other resources outside my own brain.

It’s certainly not being forced to recall the implementation details of a trie within 30 minutes, when I haven’t seen one in 5 years, unable to reference any docs or knowledge base, or use Google, knowing that if I fail I will remain unemployed.

The context of this thread is a very basic question that any good programmer should be able to bang out in 15 minutes. It's much closer to something you "should have some experience with" than "implementation details of a trie"

I would love to have an interview like that! I think the "context" here is unrealistic for most?

If by "most" you mean people in this very thread who are claiming that binary trees is some crazy obscure thing that nobody can be expected to be familiar with, then sure.