I think he is ignoring / discounting leverage as a component to wealth creation though.
Even in a world where it is impossible to make wealth without providing value, inequality will still grow in proportion to available leverage. And technology (leverage) grows at an exponential rate.
If we are concerned with inequality, then part of the equation is how do you make that leverage available to those without large pools of wealth or privilege.
I don't think customers/employees would work with company if they weren't getting at least some value out of it.
Also, just because a small group of people (customers, employees) may derive value from a particular startup company doesn't mean that that particular company, or the overall the ecosystem of startup companies, is creating more value than it consumes. The effect on inequality of the overall ecosystem is what's being debated here, and I'm not sure that anyone has a clear, data-backed understanding of which way it skews.
I don't think that's what he said. He said that inequality increases when wealth is created for the company's owners/investors while NOT creating value (or even reducing value) for everyone else (customers, the public, employees).
There are lots of examples of huge wealth being created at the expense of others without also creating value - for example: bad mortgages being bundled, obfuscated, and upsold. Tim actually proposes that bad startups are somewhat analogous to these sorts of financial instruments - i.e. there's a sucker at the end holding the bag.