It sounds very out of line of what you'd expect.
Except if Sam and Greg have some anti-compete clauses. If they join MS, they have a nice 10 billion USD leverage against any lawsuites.
I don't know, even of strictly "enforceable" I doubt we will see it enforced. And if so. I'm sure the settlement will be fairly gentle.
Edit: Actually, a quick skim of the relevant code, the only relevant exception seems to be about owners selling their ownership interest. Seemingly, since Sam doesn't own OpenAI shares, this exception would seem to not apply.
https://leginfo.legislature.ca.gov/faces/codes_displaySectio....