I doubt Einstein cared what was on his business card, but I'm sure he cared very much about being in the right career position to do the work that interested him, and to have the ability to influence his work and others.
There's only one CEO per company, so if you want more CEOs you need more companies. Being CEO of Waymo probably isn't that different from being Manager of the Autonomous Cars Division or whatever, but it sounds more impressive.
Usually, but not always. When I was at Intel, they had two CEOs. They called it "two in a box" for some odd reason.