He confirmed it verbally as well in his May 2023 hearing in Congress https://twitter.com/thesamparr/status/1658554712151433219?la...
> Even OpenAI’s CEO, Sam Altman, does not hold equity directly. His only interest is indirectly through a Y Combinator investment fund that made a small investment in OpenAI before he was full-time.
That word “directly” seems to be relevant here.