I've just looked at my 1977 edition of Book 3. It doesn't have any generic labels for Tech Levels, and hence doesn't describe TL 0 as "primitive" nor as anything else.
The word "primitive" does get used, though. In the vehicles list, for air vehicles there is a reference to "primitive types such as hot-air balloons or gliders" and also to a "primitive biplane". And there is also an entry labelled "primitive transportation" which says that
On worlds with low technology levels (0 through 3) the local means of transportation will tend to depend on beasts of burden, animal drawn carts, and watercraft such as galleys and sailing ships.
A quick review of the 1981 version of Book 3 has it the same.