Leo,
I agree with you, it is a moot point. And I think that you are correct. But I would have to say that since polyester is a man made product there is no "raw" state, as there is with cotton or other natural product.
I don't know exactly how they make polyester so it is very possible that they have the option of making it any color that they want.
What I do know is that they make polyester and polyamide, from that make microfiber cloth, which is white, and then they dye it.
One reason that I think this is an interesting topic is because I have noticed that the lighter color microfiber products seem to be softer and more plush than the darker colors. It seems that the darker colors tend to weigh down the fibers. Also, dark color towels, like red, tend to bleed. So we stay away from those.
Any more of your insight would be greatly appriciated Leo, I enjoy your knowledge on the subject.
Merry Christmas,
Ian