Humanist handwriting in the MS?

[MarcoP]

However, I think you hit the nail on the head when you say that this appears to be an unpolished reproduction of illuminations we are used to seeing in expensive manuscripts. The unpolished look combined with the naked figures is what really strikes one as VM-like, since we're not used to seeing these types of drawings often.

Upon closer inspection, though, I think the resemblance is only superficial. Sozomeno's drawing style is kind of "all over the place", for example switching freely between frontal, three quarters and profile view. Additionally, as you indicate, he is clearly influenced by standard illumination practices. There's kings, angels, humorous man-bird combinations and even scatological humor...

I believe the resemblance to be highly meaningful. Both Sozomeno and the VMS reproduce high-level manuscript layouts with poor artistic skills and basic materials: both manuscripts show complex page layout that appears to have been influenced by standard illuminations practices.
I can also see the differences: VMS illustrations are in part labelled and are quite consistent in their subjects. They do not appear to be purely decorative.
It seems to me that the two authors used similar inspiration sources and technical means to produce similar results for their different goals. Given the excellent matching of the dates (Sozomeno's ms is dated 1402), I believe there is some kind of proximity in the cultural environments that produced the two works.