White convincingly shows that both the Occamists and Luther emphasized the unity of the person of Christ over the duality. I had always read that the Occamists had encouraged a extreme Leonine Christology, but White says that's a total misreading and gives plausible reasons why Biel, d'Ailly, and Occam have been misread on this point.
Though for the time being I am suspending judgment until I get more information, I think this might be the best explanation. I was recently reading a piece by David Yeago where he argued a continuity between the Greek Patristic theology and Luther, which to me was fairly obvious. I wrote my MA thesis about it and I suggested that the basis of this is indirect influence of the Patristic quotations in The Sentences- particularly from John of Damascus. Yeago argues this way as well. Luther (as Yeago correctly observes) very likely never read any of the Greek Patristic authors directly. He simply didn't have access to them.
As an aside, it's hard for us sometimes to recognize how little information people in the 16th century had access to. When Luther read Eusebius for the first time he said "uh, where's the Pope?" He comments in On the Council and the Church (1539), that he didn't realize it at the time, but when he debated Zwingli, Zwingli sort sounded like Nestorius. In other words, he wasn't familiar with Nestorius until later life and therefore didn't actually connect Zwingli's heresy with him.
Anyways, having now read Lombard, I find Yeago's suggestion not particularly plausible. For one thing, tons of people prior to Luther in the Middle Ages read Lombard (it was the standard textbook!) and they never came up with anything other than Leonine Christology. Secondly, the quotations from the Damascene are sparse and mainly used to give information about technical Christological terminology. In other words, if one only knew John from Lombard's citations of him, then one would never get the impression that he emphasized the unity of Christ in his theology like Cyril and Maximus the Confessor.
Hence, the Occamist connection would probably make the most sense if White has correctly read their position. Again, a lot of people claim the opposite about them and therefore I would need to test his thesis. Nevertheless, I find his interpretation of the passages which he has presented to be fairly plausible and am open to this suggestion.