YC companies are likely to be in a stronger position for debt to get converted or extended than most startups. They're more likely than the general market to be good quality companies in a stronger negotiating position, and Angels aren't likely to burn YC. Plus it's fair to say that they have the cream of Angel investors, who are likely to act in a reasonable way.
I think Adeo's argument is about what happens to the bulk of the market - so applies more to all the others. YC companies have been the exception to many a rule.
I hope it proves to be wrong. But if there is a panic/bubble-burst and a herd mentality develops to rush out of the market, it's reasonable to expect many individual angels will lose their nerve and want out, at least beyond the top end of the market represented by the YC startups.