Garry didn't even relate how pitches he would have said no to got him to say yes - because they 1, used plain-spoken language, or 2, zoomed out, or 3, had a big future, or 4, knew their numbers, or 5, understood something others didn't.
I mean companies he would have said "no" to but these things made him say yes.
Quite simply, these are not the things that make people say yes.
Perhaps a better example might be this picture:
http://www.concept-phones.com/apple/iphone-7-kitchen-sink-pa...
It's a parody, right? But not exactly: many features there were explicitly requested by users.
market research is good and important. Of course I would ask investors what they're interested in, what they think about something, what they would invest in.
But that is not how you get them to invest, and although Garry does know how to get people to invest, he hasn't put it in this article at all.
I suppose the article can be useful if you read it as, "What a YCombinator partner says they want to see from a pitch." Just don't confuse it for the real advise that will get you funded. This isn't it.