This was the system in which the directory logic was formally verified: http://www.sgidepot.co.uk/origin/compcon97_dv.pdf
I agree the author probably made a simple mistake, but it is misleading to people at the "enthusiast" level who then parrot things like this as flamewar fodder. A lot of respect is owed to computer engineers at corporations that are defunct or a fraction of their former greatness (e.g., SGI, DEC, HP).
As a further example, Bob Colwell's book, "The Pentium Chronicles", is a great read and teaches some powerful lessons about how to successfully do engineering in the kind of large organizations that can scale production of a design. But if you take it at face value, the book makes no meaningful attempt to inform the reader that other companies had done Out-of-Order well before P6. It leaves a naive reader with the idea Intel pioneered OOO as well, which is no way true.
I guess I'm just (maybe overly) sensitive to sloppiness and omission leaving an inaccurate impression of the history, especially when it's so easy these days to fact-check.
Anyway, the article's author likely made the mistake of thinking that multisocket implies NUMA. It is an easy mistake to make for those who do not know the details of how systems are implemented.