Only if you're absurdly literalist. In British English that would be immediately understood as "not very accurate at all".
“Not completely” seems to clearly indicate that it is not 100% accurate which seems worth clarifying only if the base assumption is that it’s very good.
What I’m saying is that this is almost certainly completely untested and entirely reliant on the fun game mechanics used to simplify the experience of playing Cities: Skylines. Like, iirc, the game does not implement any sort of rush hour logic.