I'm not quite sure what your point is. You said "best co-founders are those who you've got some history with, who you know and trust. That doesn't happen overnight"
I agree but then how do you start it in the first place ? Isn't the point of startup school or dating school is to connect people and then from that, over time you can build that history and trust and then use that as consideration whether you want them as your co-founder ?
My theory is that people are looking for people to start a company with ASAP, rather than 4-5 years in the future after they've worked together for a while.
But who knows... I'd be curious to see actual data rather than supposing.