I'm sure there is a better, more eloquent way to explain this..
You wouldn't really call it a bottleneck, but the GPU is the limiting factor so in a way it is a bottleneck. It wouldn't be an issue though. That's where you would want your limiting factor as it would give a steady framerate; as apposed to having a better GPU than you do CPU, because that would cause larger framerate dips. It's usually better to have more CPU than you do GPU, but within reason as to not waste money on more CPU than you need.