I must agree, you are right, GOS is only on Pixel phones.
But we have to keep in mind that /e/ has a lot of problems, the only one solved is sending data to Google. The security aspect of the OS is problematic and some key elements of a privacy seem questioning (AI integration, commercial collaborations, ...).
Fix: IA => AI typo and various English errors.
Like what problems? I am using /e/ daily for myself and my family, and it's working like a charm.