A large number of those present-day Googlers are ex-startup-founders.

I've always found it somewhat silly to identify people by their employer. I was a random startup employee at two companies. I was a founder at one. I am currently a Googler. I wrote some open-source software in the interim (which reminds me, I need to go stick a license file in one of those projects because another present-day Googler wants to use it for an internal project). Which category would I fall under in your false dichotomy?

Anyone remotely interesting will have a variety of experiences in their career; some will be at startups, and some will be at large established companies.