I hope it works.
But I'm skeptical, for the reasons given in the article. Still, maybe it can be useful as a first 'booster' stage while it is still low in the atmosphere. If the engine could be configured so it smoothly switches over to an onboard oxidizer after the surrounding atmosphere gets too thin to breathe, then it might be really useful. Still, for a complex system to operate well in two totally separate environments is an engineering challenge.