The Book Switch Theory

[asteckley]

With this definition of hard evidence, your diagram would be yellow for the majority of manuscripts until the point they show up in the modern record.

I don't think so. 
I too noticed  that, in my diagram, there happens to be a correlation between green blocks and modern-ness of the particular information. But that is not the important aspect that actually distinguishes them as "hard evidence". It is the fact that there is a multiplicity of sources for the information in the block along with the observations coming from reliable/authoritative sources. That is true of each of the green blocks, and not true for each of the yellow ones.  

For example, the C-14 testing was done on multiple samples, and the technique is a well established, reliable scientific test (carried out by a professional lab)  The fact of the VMS being in Wilfred's hands, then Ethel's, then Anne's, then Hans', and then Yale's are all supported by multiple witnesses and the reports are of little doubt.  

Now the fact of "de Tepenec" is certainly authoritative -- we can all see it right there on the folio page-- and it's presence and visual details have been "tested" in various ways by multiple people. But the connection of the signature to Jakub Hořčický in particular, cannot be said to be multiply sourced, and it is only an inferred identification as well. And, additionally, there are specific observations that introduce some doubt on the authenticity of the signature. Likewise, the "fact" of the Marci Letter ever even being colocated with the VMS (let alone attached) has a single -and dubious-- source (Wilfrid Voynich).  That is all without going into the various uncertainties associated with all the yellow blocks surrounding the Kircher Letters, which we've discused before.