I would say that the information from that site are wrong, about the brand name anchors I think that he considered the money keywords and money keyword percent is recommended to be smaller than 40%, and about generic keywords they recommend 20% which is totally wrong.
The generic keywords should be minimum 60%, most of SEO experts use 80-90% generic keywords to make the backlink profile as natural as possible, many people write a lot of things about anchor text, but they never make any tests.