Every discussion about this subject has always the same problem: terminology.
Are we calling “UI designers” just that people creating the final visual design? Then… someone sketching an interface… is not designing the UI? Really?
Bonus: “UX designer” is not a role: http://www.webdesignerdepot.com/2016/08/im-not-a-ux-designer-and-neither-are-you/
I’m sorry, but I feel we are always arguing about the sex of angels.