It is probably the best that can be expected from journalism, where the writers must accomplish what research they can in a short space of time. (Perhaps the video documentary explains things more thoroughly.)
The article fails to really prove its thesis. It states that the true genius of D&D's creation is the creation of
RPGs, regardless of the particulars of the game or how much of it is written down. If that idea is true, then why stop at Arneson? Why not say that David Wesely is the true creator of the
RPG, or that it was the product of groups instead of a single individual?
For instance, the following is from the Wikipedia entry on Chainmail: "A set of man-to-man combat rules (for 1:1 figure scale), ultimately deriving from a contribution to Domesday Book #7. Gygax unfortunately lost the name of the contributor, and thus the rules were published anonymously. The core of these rules became the Appendix B chart mapping various weapon types to armor levels, and providing the needed to-hit rolls for a melee round."
Combat for individuals (instead of units) is a pretty big step in the evolution from wargames to
RPGs, but its progenitor has been lost to the ages. Maybe we should credit this mysterious figure with inventing it all.