I like to think if you invest $10s of billions, you get to at least have an opportunity to discuss major items like this, even if you don’t have legal veto.

While we don't know the specifics of the arrangement (under what circumstances Microsoft can back out of the deal), I'm sure they can make it challenging for OpenAI to continue operating at scale when they're reliant on funding (most of the 10+ billion dollars hasn't been transferred yet) and access to unlimited compute. This makes them stakeholders even if they don't have seats on the non-profit's board.

Microsoft obviously doesn't want to pull the plug on OpenAI, which is why they're pressuring the board to rehire Sam. If the board was truly independent and didn't answer to any other stakeholders, why would they even be talking to Sam right now?

Well, it appears that it was relevant. Sam Altman is CEO again.