I've submitted my application as a single founder - not because I want it that way but because none of my friends have the freedom for a venture. Does YC do match making (if they see a good fit) or this something you need to specifically request on the application?
We don't. We think it's much better if cofounders have some sort of shared history together.
My two most successful lab final projects in college were randoms. One of them won the annual award for best undergrad lab project, and the other won the in-course competition. These were late-course groupings, after as many as half of each class's starting participants had already dropped out, so it was already pretty selective.
Bad: We didn't know each other ahead of time. There were always weaker and stronger participants. In one 4-person team, one teammate just completely flaked, but the rest of us stepped up.
Good: We didn't have relationship baggage that could have come from partnering with friends on a very stressful project. I think it really helped us focus on the projects. We were thrilled with any success.
I used to think it was just good luck finding outstanding teammates. But perhaps it was because they had already independently made it through the hard first half of the course without having close friends also enrolled in the class. As a counter-datapoint, another course had a lottery-based grouping, with no pre-harrowing, and my teammates and I never gelled.