Assuming your whiteboard session is a good test of basic CS proficiency, the real question is "does basic CS proficiency correlate with effectiveness at the job?" - if you're like Google the answer is probably yes, and if so you only have to have tolerance for false negatives. Given enough applicants that's clearly less of a problem than false positives.

My other point is that some companies might find there are other qualities they're looking for that occur in the pool of people they pass on. That's what's really worth looking at, I think - all the while being careful not to mistake "good cultural fit" for "promotes long term monoculture".

But the question he is raising with the false positives is that it is a gating mechanism for what? The ability to talk shop on a white board?

I'm assuming in my answer that the interview happens at a shop that cares about CS proficiency. (Mine certainly does ;)

If I have a false positive (i.e. you seem to understand CS but don't fit the company), it's not like the CS question is all that's asked. It's the launch point for a deeper discussion. That means a false positive hopefully gets caught in that later stage, but deep CS knowledge is sine qua non.

If that skill (knowledge of CS) doesn't matter to your shop, then yes, you shouldn't use it for gating.