Did he? I'm very skeptical of that since I read every single one of his essays and followed his talks. They were one of the reasons I decided to transition into software in my early 30s.
http://www.paulgraham.com/hiring.html
"Or more precisely, I think few realize the huge spread in the value of 20 year olds. Some, it's true, are not very capable. But others are more capable than all but a handful of 30 year olds."
So I am wrong
edit: I found where I am attributing Graham from. I am still wrong, but here is the context:
"Venture capitalists have a notorious bias against older founders—“older” being relative in youth-obsessed Silicon Valley. “The cutoff in investors’ heads is 32,” Y Combinator co-founder Paul Graham (now 53) told the New York Times in 2013. “After 32, they start to be a little skeptical.”
https://www.nytimes.com/2013/05/05/magazine/y-combinator-sil...
“I want to stress the importance of being young and technical … Young people are just smarter. Why are most chess masters under 30?" he asked. "I don't know… Young people just have simpler lives. We may not own a car. We may not have family."
Of course, he said this in his twenties and he may have changed his tune. As far as I know, he hasn’t handed the reigns of Meta over to a twenty-something just yet.