I've seen that in oils every so often (although not in Motorcraft) Mostly in GTX years ago.
I always figured it was one of the additives that had setteled in the bottom of the bottle while the bottle was in storage, waiting for sale.
Watching old time mechanics, I saw that they would always shake the bottle to mix the additives, before pouring into the car.
(I even remember them doing that when oil came in metal cans, and later, in cardboard cans, before plastic bottles).