re:
You are still enrolled in the Preview and receive any new updates by MS. It doesn't just go away when an update is released. (in this case, 8.1 Update 1 is likely on your phone unlike normal 8.1 that is on phones with Cyan.)
I wouldn't recommend uninstalling the Preview app unless you want to disable future Preview updates. (You CAN, but I don't really see why unless you want out.)
I can't spend too much time on this, but I hope that helped...