That is like saying, people who self-select to go to the physics department go there only to be with other physics students are and that it, "doesn't have anything to do with the teachers, [or] the curriculum."
What is more likely, is the school does an excellent job affording students the opportunity found successful, venture-backed companies. Similar to the way the Physics professors and curriculum afford physicists the ability to be good at physics.
The fact the article highlights this opportunity for other entrepreneurially minded people, who may want to attend in the future, is exactly what the data in the article is supposed to do.
Stanford also does a good job of helping interested students with those things. It’s just larger and more diverse, and also includes students who want to be judges, literary critics, historians, medical doctors, mathematicians, journalists, school teachers, etc.
If you looked only at the subset of Stanford students with similar interests and backgrounds to Olin’s student population, you’d probably end up with a similar distribution of outcomes.
There's a qualitative difference, though, in being in a place that is full of mostly people who don't share your interests/goals of founding startups (Stanford) versus those who do (Olin). E.g. there's more gay people in Dallas than in San Francisco (owing to population size differences), but the latter is still a much better place to be gay because of the concentration.
I don't agree, I think it's more likely than not that a school specifically designed to foster a particular type of thinking is at least somewhat more effective at it than others. Just like Stanford is likely more effective at developing elite researchers.
I don't think there's nearly enough information to determine that confidently, but we're simply talking about beliefs at this point.
Doubling down on this point, there are undoubtably people who went to Olin not planning to be a founder, who decided to be because they knew someone else who was a good role-model for them.
Does Olin produce / graduate founders at ~5 times the rate of Stanford? Yes - no bias.
Is the effect size due to self-selection? Likely at least partially.