I have not been at a single company that anonymizes its interview pipeline. Are there some examples of companies that do this?

I know Interviewing.io does, but they don't have the final say in hires. They just forwarded candidate to companies, which were under no obligation to maintain anonymity. Ironically Interviewing.io's anonymity is why Meta refused to work with them: https://interviewing.io/blog/i-love-meritocracy-but-all-the-...