> I've heard of people at big companies who conduct thousands of interviews a year

I don't disagree with the rest of your thesis, but this seems off by an order of magnitude. They would have to conduct 4 interviews every working day to reach even 1000 interviews. Counting the time needed to write feedback for every interview, that person would be a full-time interviewer who occasionally writes software/does product management/project management.

Unless you're speaking of a small group of people who conduct disproportionately more interviews than everyone else (Pareto distribution) - a dozen interviewers could easily rack up 1000 interviews between them.