Did François Viète Break a Polyphonic Cipher?

I reported Paolo Rosson's full decipherment of two letters in a polyphonic cipher in a new article, "An Intercepted Report of Henry IV's Upcoming Attendance at Mass in a Polyphonic Cipher". When I identified the key from deciphered materials back in 2017, I reported these as undeciphered. The fresh decipherment reveals reporting of the prospect of Henry IV's attending Mass.

Rosson noted that these were among the intercepted letters but were recorded as left undeciphered. Probably, because the letters to the Pope and the Bishop of Lizieux from the same date were deciphered, deciphering these was not considered important. Since Rosson provides the full text, I hope someone will compare it with the known letters to see if there is some new content. (Maybe AI can do such a specific task?)

From the viewpoint of cryptography, it is wondered who deciphered the letters to the Pope and the bishop. It is exciting to speculate whether it was François Viète.