Read the article again -- it clearly says that this discovery is the "smoking gun" on the question of how many eggs dinosaurs (or at least this lineage of dinosaurs) laid at a time, *not* on bird evolution in general:
Previous discoveries of dinosaur nests of eggs or clutches have appeared as though the creatures laid their eggs in pairs but, until now, scientists had no proof that was the case. In fact, many denied the possibility that eggs were laid in pairs. Renowned dinosaur hunter Philip Currie of the Royal Tyrrell Museum in Drumheller, Alta., pointed out that the only resolution to that dispute was the remote chance of discovering eggs inside a body cavity. Uncovering this oviraptorid specimen, he said, is essentially like finding the "smoking gun."