Is it odd that the Shop Manual does not mention a gasket or the spacer/insulator?

The Master Parts Manual refers only to a gasket between spacer and carburetor.

I always use a gasket between carburetor and insulator (with the cut-out properly oriented).
I have sometimes used a gasket between spacer and manifold (if the mating surfaces were not real smooth).
I have never had a leak when I did not use a gasket between the insulator and clean/smooth insulator and intake nanifold.