Concluding: if you lay your content out in an F pattern (navigation bar, plus rows of content) you'll see an F pattern emerge. If you don't, you don't.
NNgroup has never claimed that the F-pattern will emerge on all types of layouts. Of course, you get a big heat map blob if you include homepages, gallery pages, product pages etc.
The pattern emerges when you have a classic article page. People read the headline, then the first paragraphs and skim the text further down the page. And voila - an F-pattern occurs.
Perhaps. I don't think this post isn't meant to be a critique of NN, but rather the fact that people apply the F-pattern concept as a golden rule for all types of websites. To my knowledge, this is the first time actual (larger scale) data has been published rather than just anecdotal examples for individual pieces of content.