The name Pontiac was introduced by General Motors but it was actually a conglomeration of several coachworks that were placed under one roof, and out of those Pontiac survived as the dominant brand. But either way it has no bearing on what constitutes a division and the brand. Both examples are brands offered by a parent company, whether that brand existed on it own before being purchased has no bearing on making it anymore antonymous from its parent company. As far as being right, they did not make a split grill they have always been split grills since the 60’s. Every Pontiac has a split grill, whether it is functional or not.
Finally not all Pontiacs have shared Chevy engines, that did not occur until the late 70’s and early 80’s. In fact some of today’s Pontiacs use an engine from Opel or even Holden. Pontiac only has one model that currently shares the similar body components as Chevrolet. Glad to clear that up for you.