I do think it's worth looking at a few of his other posts (I'm a fan) to lend some credence to this one speficially. The more history-focused (so not aimed at worldbuilders) pieces are consistently well-sourced in a way that most blogs aren't, and he has a pretty long history of this same level of care.

Does that make him infallible? Of course not. But it does mean I'm going to give him the benefit of the doubt here.