I work at Google and have absolutely no clue what he's referring to.
My best guess is that it has something to do with the permissions you give Google if you add a work profile/account to your phone. But that isn't required.
You can imagine different tiers of security, where a work profile gives you minimal access to corp while a fully managed setup gives you more substantive access to corp resources and allows a company to enforce more security and visibility into the client device.
That makes a lot of sense, and a legitimately personal decision. Some people don't want to share root access on the personal phone with their employer. Other people don't want to carry a separate phone for work.
