"Sam Altman has seen the early stages of lot more unsuccessful companies"
Sam Altman has experience with a particular group of companies. A small subset of companies out of a huge set of people who do business. In a wide variety of places.
This writeup certainly makes some good points but it is specific to companies of a certain type and Sam has not qualified that at all in his post.
"than pretty much anyone has seen companies at all."
I've been observing companies (as have many other HN readers) since before Sam was even born. (I started my first company right out of college and that a very long time ago.)