The conversation is about the dropbox founder quitting his job to wok on dropbox part-time.
The problem I see with pg's logic is that the founder and YC are not betting the same value on the company. The way I see it, YC is asked to bet some money, but the founder is asked to bet everything they got. If YC was asked to bet everything they had on that one company, they'd say no. In that case, having a plan B is not a sign of lack of resolve, it's a sign of sanity.
But I'm probably missing something. I really don't have the whatsitcalled, entrepreneurial spirit. It all looks like gambling to me and I hate gambling, especially when the odds are stacked against me; which they always are, otherwise it's not gambling. So I guess I don't get it.