But more importantly, in modern birds, the uncinates act as levers that, together with muscle action and sternal ribs, actually raise and lower the sternum during respiration. The "pump" action of the sternum has long been known as a major factor in avian breathing, but it's surprising to see the uncinates actually facilitating this movement. But that's not even the focus of the paper. Rather, Codd et al. merely strive to understand the phylogenetic consequences of uncinates in the Theropoda, and what that might mean for theropod activity levels.
The paper is actually disappointingly short, especially when you realize that it could've actually been shorter. It turns out that uncinate processes have a fuzzy preservation record. This should not surprise us, because they are attached to the ribs with cartilage, and the processes themselves were thin, strut-like bones. At any rate, they are only known with certainty in Oviraptor, Citipati, Khaan, Velociraptor, Deinonychus, and Microraptor. Thanks to phylogenetic bracketing, we can pretty safely conclude that the common ancestor, at least, of Oviraptor and Deinonychus also had uncinates. So that means we can expect to find more complete remains of, say, Nothronychus with uncinates, and troodontids, too.
In modern birds, the sternum's keel provides a key muscle attachement site for respiration, but Codd et al. suggest that, because non-avian maniraptors did not have keels, they may have retained their gastralia for essentially the same purpose. Short paper, but these are things that needed to be said!