Regardless of that, the size of "UNTRAINED muscle fibers" means abolutely nothing to bodybuilders.
I was a kid with small muscles. Does this mean that somehow tells you how much those small muscles could grow?
Of course not.
If the size of untrained muscles mattered at all, everyone would be limited by the size they started with.
The OP apparently didn't understand this....which is why "a little knowledge" can royally fuck you up.
That is why lay people can make mistakes when trying to look at scientific research with no formal education.
I know they hate to hear that, but it's the truth.