I don't think this is true. The vast majority of closed source programs are created in house for in house use. No one is ever offered it publicly so no one buys it either.
It's hard for people to see the scale though because there is usually no central repository.
Also, I'm sure everyone's seen a closed source project that went nowhere?
It's only when you make a full system that the end user can get value out of that you get into the scenario he outlines. Somewhere in the middle in between the simple code dump and Firefox, open source tends to sink into a quagmire where it looks like a product but it's not supported like a product. And the only good answers then seem to be "go small" (impose LOC limits and hard constraints on features you ship so that maintenance drifts towards stability) or "commoditize" (become part of someone's product in a way that gets you paid).
So the author is wrong to compare all software on Github to closed source software he's heard about. Those "measurements" are completely different.
I think he's applying closed source's rules. A closed source project is a failure if no one uses (ie, buys) it, since it represents a development cost that wasn't compensated. Not so with open source. I don't suffer if no one uses my project, and the existence of my repositories doesn't detract from anyone else's work.