I'm not trying to downplay the importance of co-founders so much as try to show people what they need to be looking for in cofounders as well as what they need

I'm not trying to downplay the importance of co-founders so much as try to show people what they need to be looking for in cofounders as well as what they need themselves. YC has every right to want multiple founders, but for someone who doesn't get in, or doesn't apply, this information could help them know where to focus their time.