You seem to be very knowledgeable about this field so I won’t try to change your mind, as I can tell you’re more familiar than I am. In fact, I also have my own reservations from reading the actual paper. The same authors actually have another paper in the same topic with the same material with a preprint out after this one, and I doubt someone would salami publish results as marvelous as these ones instead of just going for a single massive impact factor journal.