It depends what the conclusion in question is, whether selection bias is a factor.
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.
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.
I don't think there's nearly enough information to determine that confidently, but we're simply talking about beliefs at this point.
This is not dissimilar from the old boy network that makes Washington and Lee the single university which most increases your median earning potential. (See https://en.wikipedia.org/wiki/The_Economist_Magazine%27s_Lis... for where I got that from.)
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.
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.