Okay, so pg posits that the people he finds and helps to become billionaires get there because they have some special insight into a solution to something people need.
He's definitely right that it is valuable to society that people who have such insights are given the opportunity to build their solutions. We all win from being in a society where more of our needs are met.
What's perhaps slightly more dubious is the idea that, by bringing that insight, the person who has it deserves to own a billion times more of a vote in how our society is run than the average person.
Because that's what wealth, what a dollar, is: it's a voting share in how society spends its time and resources. As the owner of a dollar, you get to decide whether people spend their time growing and picking and shipping some plants and making them into some bread and then putting together a sandwich for you, or if you'd rather they dig up some rocks, extract some silicon from them, imprint it with complicated patterns, and then construct it into a device you can put in your pocket that lets you see photographs of influencers.
The pg thesis here is that instigating an idea, creating something that doesn't exist, is not inherently exploitative. That is true.
But what is perhaps arguable is, that in delivering on that original founder's vision, one which attracts many of those votes for how society should spend its time from many people, and thus accumulates billions of dollars of revenue - that many people other than the original founder end up creating the organization and building the factory and working the machines and writing the software and actually serving the customers to make that solution real - a bunch of people other than the founder are involved, and... well, if you choose to structure the rewards of that organization so that all those billions of votes in the future of society accrue to the founder, while only thousands of them accrue to the people who do the work of making it happen... that it's possible to construe that distribution of rewards as maybe slightly exploitative?