i have never heard of a adhesion promoter between base and clear coat eather. i think the rep was giving you a tall tale.
i think your problem with the clear delaminating from the base coat was using two incompatible products from different manufacturers.
if a body shop is DUMB enough to use products from different manufacturers in there paint jobs they deserve all the problems they get. you should ALWAYS use products from the same manufacturer to garentee the products will be compatible with each other and you can have the manufacturer stand behind the products.
if it wasn't a incompatibility problem you had a problem of applying the base coat to dry. when you do that the paint can't chemically stick to the surface underneath. it's like trying to apply paint with a layer of dust, that can blow off with air pressure, between coats of paint.