An eight doesn't mean you're an idiot, and it doesn't mean you have trouble speaking or stringing sentences together - Blackheifer's scale is pretty accurate in most ways, and ultimately speaking, in a video game, they shouldn't be enforcing dialogue restrictions or changes on you unless you're at a 5 or below.

It would be nice if 6-8 presented the same dialogue options but in simplified language - not infantile or stupid, but just using plainer, simpler language... but considering the limitations we're already seeing as a result of them fully voice acting everything, I'm extremely doubtful that we can hope for that level of nuance.