However, I also wanted to point out that "Distinguished SWE" != "IC". There are plenty of L8/L9 Google employees who are on technical ladders but whose jobs are mainly -- or solely -- about people management. Those people have Principal/Distinguished X as their title.

This was very common in the olden days and remains true for long-tenured employees. Google's been moving away from this model by requiring that employees move onto a management ladder once their job is mainly about people management. However, I doubt anyone would want to piss off all those Principal and Distinguished SWEs/RSes by forcing them onto a different ladder and replacing their titles.