I don't buy for a second that enough employees will walk to sink the company (though it could be very be disruptive). But for OpenAI, losing a big chunk of their compute could mean they are unable to support their userbase and that could permanently damage their market position.
Which does not say whether microsoft was open to the idea or ultimately chose to pursue that path.
i've seen similar with the cloud credits thing, people just pontificating whether it's even a viable strategy.