It sounds like he was worried that in the best case the manager would (perhaps unintentionally) get credit for his killer work and in the worst case the manager

It sounds like he was worried that in the best case the manager would (perhaps unintentionally) get credit for his killer work and in the worst case the manager would actually hamper his work by trying to control him too much. It sounds somewhat petty, but I can sympathize because the company I work for is going through a similar transition and I've seen the strains that even a single extra manager can have on communication. If the CTO is the one who approves your raises, and now the CTO's opinion of you is not shaped by you but by reports of you created by an intermediate third-party, a lot of somewhat complex interacting variables just got introduced into the equation. If you start out at the bottom of a huge company like Google, you get used to that from the beginning. If you join a company with <=25 people and watch it grow, then you can really feel the transition sometimes.