The study indicates premature scaling is the number one cause of startup failure. Y-Combinator's results seem to indicate the number one cause of failure among its startups is kind of the opposite: the startup just kind of peters out, and the founders go work on something else.

I assume this is a result of selection bias on both sides: Y Combinator only funds extremely small startups (generally 2-3 people), and this study likely (though I'm having trouble verifying) only includes startups that got beyond this phase. Does this sound reasonable?