'69 windshield gasket...two kinds of sealer?

Glazing putty...that makes a lot of sense. Finally someone has verified that I'm not making something up. People are such information repeaters without even knowing what they are talking about.

This is directly from the 1969 Dodge service manual regarding windshield installation:
Installation:
(1) Remove all old sealer and cement from original weatherstrip if it is being used
(2) Apply sealer in fence and glass groove portions of weatherstrip. On Dart Models install filler strip in lower part of weatherstrip (Fig. 4).
(3) Apply a 3/8 inch bead of sealer cement completely across cowl top panel lower windshield frame area (Fig. 5)

Notice the part where it says "sealer AND cement" and the instructions to use two different materials in the different locations, just coincidentally how my car was done.

So in other words, if you want to use all bedding compound, fine. If you want to do a factory-correct job, then use the different materials as indicated. Additionally, it's not up to a particular member to question why somebody else wants to know something. If you know the right answer, post it. If you don't know the answer, say you don't or don't post anything at all.