I worry that the tone of the article seems dismissive of the choice that went into mapping those keys to arrow directions in vi ("That's the whole story"). As if to say it was mere happenstance that vi uses hjkl, and any other outcome was equally likely.
It seems more the case that the designers of that computer chose those particular keys on the basis of a desire for efficiency that vi also followed, so there was no need to create a new convention.
Honestly perhaps it's partly a defensive reaction about a tool I like. If so, my bad. Maybe I can't help but feel like the "article" could be perceived as saying "see, vim chose these keys simply because that's what the keyboard said without any thought toward efficiency". The idea that they're chosen for efficiency seems so self-evident that it doesn't need a flourish to reveal. It's likely I'm thinking too hard about it. In any case, it is a neat little bit of history and the link gets my upvote.
Maybe "efficiency" is implied, since folks using the initial version of vi would be used to using those keys for navigation anyway. So, I read this more as "Bill Joy used a convention" rather than "Bill Joy chose the most efficient keys for touch typists."