If we're looking at more than just computer gaming he is most certainly correct, single player is the anomaly. That doesn't make it "bad" in any kind of moralistic or judgmental sense, it's actually kind of cool what the medium of video gaming has done for our ability to play games. It's important to note, though, that gaming fulfills a psychological need for us (at a very low level it appears extremely important, i.e. games are actually required for life, not at the level of food, but for anything above managing to not quiet starve a day at a time, it is).
Historically even single player gaming performed the function of enabling social interaction. That's why we had Nintendo Power magazine, its why my buddy and I would rent a NES and some awful game like Faxanadu and play all weekend, while taking turns. How do you think we learned all those easter eggs when we were kids? We learned them socially. Why did every kid know to blow on the end of NES cartridges when they didn't want to play? It's not like you learn that from your parents. I don't think me or any of my friends every had a video game magazine subscription, but we all knew how to do that, even in our hick town.
So, while I find the wording in the article tortured, the whole article is rather ass in fact, social is part of gaming and culture, even single player gaming. The internet has proven once and for all that single player is social, look around, it'll take about a millisecond to convince yourself. The premise in the article is no more than bringing video gaming into the home where they often had to be enjoyed individually was an odd shift from something that historically was far more of a social thing (even arcades are social from his perspective: the high score list at the very least, but the ring of people around any Street Fighter machine watching one kid rock every challenger was always a common sight).
I think Yaegar proved that single player experience have a fuckton to still give, but even that is inherently still social: everyone talked about Spec Ops: The Line, and couldn't stop talking about it, even months later.