> clearly my interview would be better if I came up with the perfectly optimized solution, or gave a lecture on the options rather than trying to discuss options.

Right. And a competency based interview goes better if you have a perfect example for every question. But it isn't an auto-fail if some of your answers are mediocre

Personally though - I'd rather hire someone who is able to properly communicate their thought process over an imperfect solution, than someone who was unable to discuss/explain the perfect solution they scrawled down.