OpenAI is likely limited by how fast they are able to scale their hiring. They had 778 FTEs when all the board drama occurred, up 100% YoY. Microsoft has 221,000. It seems difficult to delegate enough headcount to all the exploratory projects of MSFT and it's hard to scale headcount quicker while preserving some semblance of culture.
I don't think what you're saying is correct though, either. All the early news outlets reported 49% ownership:
https://en.wikipedia.org/wiki/OpenAI#:~:text=Rumors%20of%20t...
https://www.theverge.com/2023/1/23/23567448/microsoft-openai...
https://www.reuters.com/world/uk/uk-antitrust-regulator-cons...
https://techcrunch.com/2023/01/23/microsoft-invests-billions...
The only official statement from Micorosft is "While details of our agreement remain confidential, it is important to note that Microsoft does not own any portion of OpenAI and is simply entitled to share of profit distributions," said company spokesman Frank Shaw.
No numbers, though.
Do you have a better source for numbers?