> So I'm neither expecting syncopation here nor am I noticing anything unusual there.

I'm not either, but that doesn't have anything to do with the point. The point is that their classification model has Lennon staying on the same note, and that happens with "The Word" if you give the importance to the highly stressed note (which, as you point out, is on the downbeat). But, partly because the stressed notes are surrounded by other notes, they are assigning the melody to McCartney.