MSFT's control isn't as "hard" as you portray it to be. At the senior leadership level they're pretty happy to allow divisions quite a lot of autonomy. Sure there are broad directives like if you support multiple platforms/OSes then the best user experience should be on "our" platform. But that still leaves a lot of room for maneuverability.
Soft control via human resources and company culture is a whole other beast though. There are a lot of people with 20+ years of experience at Microsoft who are happy to jump on job openings for middle-management roles in the "sexy" divisions of the company - the ones which are making headlines and creating new markets. And each one that slides on in brings a lot of the lifelong Microsoft mindset with them.
So yeah working within MS will be a very different experience for Altman, but not necessarily because of an iron grip from above.