Well, seroquel is an antagonist at d2 while abilify is a partial agonist. I am thinking the remaining dopamine from abilifys partial agonism might be antagonized by seroquel. So the end result is just antagonism, not partial agonism. Essentially you are on one drug, not two.
I read in someones post once that abilify monopolizes the d2 receptors, meaning taking another ap with abilify gets canceled out by abilify. Abilify has tight binding at d2 almost at the level of haldol.