I asked my cofounder about this (she's mentioned in the article). She said "This occurred to us. We're a school of engineers - we talk about sample sizes a lot"?
Hypothesis 3 - that alumni or faculty are supportive - applies to any number of schools. Need more to show this is a distinguishing factor.
Hypothesis 2 - the school encourages growth and "spiral learning" - is vague. Going to need more evidence to prove this is a unique characteristic of Olin.
Hypothesis 1 - the school attracts students with a certain risk profile - is precisely the parent's point about selection bias. There is a healthy discussion of this above.
Your requests for info are fair, but for 2 and 3, it's not hard to find hints of evidence with a mere Google search.
I did not go to Olin, but knew about them from when they were fairly new. Their very existence from the first day has been to produce entrepreneurial students, and their curriculum has always reflected that. IIRC, they don't separate courses based on "engineering" and "entrepreneurship". They aim for every course they teach to be a mix of both. Very few pure "theory" courses. Taking a course in communications? You will learn both the theory (Shannon, etc) and you better build something significant by the end of the semester.
Honestly, from the comments here, I'm surprised at the level of doubt. I thought more people here would be familiar with Olin.
(None of this is to say that they are or are not effective in 2 & 3, but it is a foundational principle of theirs, and I imagine a metric they track - as opposed to typical top schools that claim 3 but are pretty bad at it).