This costs money. As long as Google receives plenty of acceptable candidates, false negatives are free.

(Assuming they get no false positives, which, thinking about it, is a big assumption)

My presumption was that, for whatever reason, they couldn't or wouldn't do screening at this level by technical interviewers. Obviously having a technical person do the interview is always better.

I may have gotten a technical interviewer because I can list a half dozen people who know me who work at Google, most of whom can directly vouch for me.

Not sure why the OP got an unskilled reviewer, but if they didn't list references inside the company, they may have been thrown in the "random unknown applicant" bucket.