That's mixing things up. Imitation isn't the problem here: clones happen of all successful products, and that's a good thing.
The problem is fraud. These titles and authors (and sometimes cover art) are deliberately similar to existing products and appear designed to catch sales from people who aren't paying attention. That's not the same thing at all.
I dunno. While I'm not a connoisseur of that genre, some of the imitations do seem to be deliberately designed to skirt just this side of the line that would get them sued and/or indicted.
"Yeah, we'll call ours...Moonlight, and we'll make the guy a zombie, no a mummy!, not a vampire..."
Clearly the "books" in the referenced article are way over the line, wherever it is. That's why I said "not quite as blatant". However, I don't think the position of that line is quite as firm as you're suggesting.
I still think you're confused. Making a Twilight knockoff about mummies isn't going to get you sued or indicted. The content, in fact, really doesn't matter. The point is are you deliberately trying to confuse buyers who want Twilight into buying your book instead by mistake?
That's just not a feasible attack vector with brick & mortar stores, where you can't draw eyeballs without paying for very expensive off-shelf displays. But on Amazon, you can game the search results to put up a page that looks to an uninformed buyer like the genuine product. That's fraud, or nearly so, and it's absolutely not what the me-too publishing world does.
The problem is fraud. These titles and authors (and sometimes cover art) are deliberately similar to existing products and appear designed to catch sales from people who aren't paying attention. That's not the same thing at all.