I think the upper middle managers were actually hit harder in this layoff than the higher level eng ICs.

Anecdotally, this rings true.

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.

The flipside is that it's very difficult to get promoted as a manager. As an IC you can at least show some skills to prove that you deserve to be at the next level. A manager can usually only get promoted if there's enough scope or if there's an opening at the higher level (eg. senior manager left).

You should check the percentage of LN for N>=7 for ic and manager track.

From my experience it’s the exact opposite

For sure. At Google, L7 ICs are rare. L7 managers, not so much.