I would need to see a citation for this. I work with digital marketing folks a lot, who are well-versed in things like SEO, and the general trend seems is toward shorter and more frequent content. That's not to say that I don't write a longer piece when the content warrants it, but for written articles/blogs/etc. 800-1000 words seems to be fairly common. Certainly there's also something of a trend from giveaway long books to 25-50 page ones.