The fact that some of the VM letters are similar or identical to characters used in medieval or Renaissance shorthand schemes has led people to believe that either —
- The author was familiar with shorthand techniques (“weak shorthand hypothesis”), or that
- These symbols were used as a shorthand to abbreviated letter sequences in the VM (“strong shorthand hypothesis”).
I think this is jumping to conclusions. After all, there’s only so and so many different characters one can compose from a limited set of pen strokes that I’d be surprised if someone who wanted to purposedly*) invent an alphabet wouldn’t come up with shapes like “I”, “O” or “X” (even if they meant different sounds), because they can conveniently and quickly be drawn and are readily recognizable.
Even in period, the shorthand symbol “4” (resembling EVA “q”) was also used to denote the number “4”; apparently both meanings were independently developed.
*) Historically developed alphabets might of course be different.