Gordons sold out around 2016 to PolyOne Corp., who have since changed their name to Avient.
The glass streaks are a function of the size of the "thread" or "tow" of the glass fibers in the matrix.
I would imagine its costly to re-thread a pultrusion machine with fine tow glass, just to get a clearer product.
Here is a promo video, but it shows and explains the process well.