The point is that they grew their business mostly out of revenue. Yes you can get into a technical discussion of what a self-funded company is, but it generally misses the point. Setting yourself up so that you can be sustainable out of revenue at times requires a different approach and mindset which is at the core of self-funded companies.
But bootstrapping has a binary definition. You have either raised money or you haven't. And there is a huge difference between $500k and $0. And I don't say that in the theoretical sense. I currently run a bootstrapped company that does $10m+ in revenue and $500k is still a huge amount of cash for us that would change the way that we conduct business. I can't imagine how big a difference it would have been in the early years of the business.