I'm not OP, but when I've experienced this, it's very similar to something like "I've seen a million heist movies, but absolutely could not steal shampoo from a CVS". There's a very big difference between talking about doing something and actually doing it; there's a level of executive function that's required.

More specifically, you make so many small executive decisions when coding. Naming, how functions and classes are designed, which file/module this goes in, is this already tested, oh I found an unrelated bug, do I make a ticket, a new PR, or include it in this one, etc etc etc. The only thing I've seen that can answer those questions is homework--maybe previous work, but homework is better.

But I think you're remiss if you're not asking your senior engineering candidates how they make those decisions, not because the answers to relatively trivial questions are important, but because you should know--and they should be able to articulate--how they make those decisions, and they should know the pros and cons of their approach and other approaches.