Didn't read the article ... but when an author makes a statement like this ... the red flags go up.
I think the excerpt provides the context of that statement. I interpreted it to mean that this is the first time they’ve done a non-sampled approach and looked at the whole thing.
"They looked at 1.2 billion places in each genome where such chemical markers [epigenomes] exist. The analysis was unusually rigorous — and therefore unusually revealing, Ecker said. Earlier studies examined representative regions in the genome, rather than the whole thing."
IIRC, the last time I checked, there are just a little more than 20,000 genes in the human genome. This is the first time anybody checked for these epigenetic/epigenomic differences, IIRC. They happen as an organism matures after fertilization. That's the reason it's rigorous.