Palatino 766 pipes, pools, cliffs, streams... (by Taccola)

[MarcoP]

is it really true that the later copybook Palatino 767 contains imagery that is exclusively found in Taccola's Palatino 766, but not in his earlier works Book I+II?

Who said that? I cannot find it in the passage you quoted.

According to You are not allowed to view links. Register or Login to view., Pal.767 also contains material from Books I and II.

EDIT:

As noted by Gentile (1885) and Jähns (1889), the manuscript [Pal.767] contains a copy of Palat. 766. It also contains material from Books I and II and the Mill, Pump, and Gear Complexes. In all cases the copying is close. The manuscript copies Books III and IV in a form independent of Urb. Lat. 1757 and in much wider selection, while it copies large portions of the other contents in a form that repeats peculiarities of the Urbino codicetto. In particular, many deviations from Lat. 197, found in the Urbino booklet, reappear here. The impression arises that Palat. 767 is based on Palat. 766 and Urb. Lat. 1757, not Lat. 197.

So they apparently believe that 767 derives from the "codicetto" by Francesco di Giorgio Martini Urb.Lat.1757, a copy of Taccola's Books I and II autograph Lat.197. They say it appears to derive directly from Taccola's autograph Palat.766 for Books III and IV.

Palatino 767 draws on Taccola's works, but in my opinion is not a direct copy of Palatino 766.

Personally, I have no problem believing that this is a direct copy, but I am not an art historian.