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."