Did he actually ask to reduce his position? As far as I'm aware, being a CEO is never based on hours worked, and there are plenty of other CEOs with multiple commitments.
The way the tweet is phrased makes me think he was asked by the board to choose, so I guess a more appropriate analogy would be:
I'm employed by a company, I start a side gig which I spend 50% of my productive time on, my boss eventually tells me that they need someone in my position to be a proper full time employee and I need to choose. I respond, "okay, in that case I resign".
There's no difference between the two analogies in my eye, they're the same except that the first is about asking permission while the second is about just doing it.
