What is special about Voynich plants?

[MarcoP]

Thanks everybody for your great comments! I hope to collect some more ideas, then I will attempt a synthesis. 
Ellie, I agree with what you write about the Voynich manuscript being consistent with the other sources. Yet it has its peculiar traits (as all manuscripts do). Since I know you have seen many, I would appreciate if you could share the details of some of the differences you find relevant, if there are any.

I attach an example of Plantago with an accompanying animal (quite frequent, but absent from the four manuscripts I chose from comparison). This is from BNF Lat 17844 (Italian "alchemical herbal", 1440-1460).

I have updated the attachments in the first post, adding plant names for easier reference and using a slightly higher resolution.