This article mentions several open resources, but it doesn't mention OA itself. When it briefly discusses open resources, it focuses on digitized public-domain books. It's silent on OA journals. It's silent on OA repositories. It's silent on open data. When it mentions journal literature, it's only to suggest that independent scholars might buy temporary memberships in JSTOR.
It wouldn't be hard for someone to write a better version of this guide. But why was it evidently so hard for the to realize that a better version was needed?