I think what the OP is hitting is the difference between being able to explain something and being good at it. With a deep enough interview process you’ll find

I think what the OP is hitting is the difference between being able to explain something and being good at it. With a deep enough interview process you’ll find people who know what they are doing. But it won’t tell you anything about their practical coding skills; it won’t matter if you are hiring an architect, but if it’s for a main developer you’ll want a decent level of productivity, proficiency with the tools, application of best practices and reviewing skills. Those aspects are a lot easier to understand with actual code produced.