I HATE when aquarium books give info like that on betta. I was going to buy a lovely book.. until I saw "male betta splendens can be kept with 1-2 females happily" and "a plakat is what they call a white betta in Canada" (WHAT? o-o).
They also said doing regular water changes once every 3 weeks would help a sensitive species like a panda cory survive (probably the most difficult common cory to keep)...
If that info was in there and I knew it was wrong, I don't even want the book, for fear of how many other things are wrong.
So yea, even published books can be wrong.. a lot of "fish" people who never kept betta throw them aside and just write some random stuff that's possible with other anabantids (like gourami).