I am using DAP latex window glazing to repair some old windows. The instructions say to use a latex primer on new wood or an oil based primer on old wood. Why the difference? Also, what about using a shellac based primer, such as BIN, or even linseed oil, as is used with traditional putty?

The Zinsser BIN primer is an INTERIOR and "spot" Exterior primer.......Shellac is not "waterproof" and not recommended for general Exterior use......

The Linseed Oil while appropriate under an Oil based glazing would not allow the latex to bond to the window properly.....

The Oil-based primer recommendation is because it will bond to any old finish that may be on the old wood.......and the latex caulking(glazing)will bond to the primer.....

And the Latex primer on New wood with the latex glazing is the easiest to apply and clean-up....Fast to dry without any existing conditions to foul the primer.......