I can't remember if it was Ray at BCY or someone else who told me about the white...it was a long time ago...
I think at best it's bleached? Generally the white is a tiny bit smaller in any of the BCY materials, at least the ones I've handled (B-500, B-55, 450+, Dynaflight '97). You can strip the wax off of white and you don't get white wax--strip it off of any color, the wax will be that color. I'll try to remember to ask again.
Never heard that white was stronger. There's so many old wive's tales floating around this sport, especially with strings, it can be hard to keep up.
Chad