UX is not a specialism, it’s unwieldy generalism. In the Silicon Valley (where I’ve lived and worked for 25 years), User Experience was a term coined by Don Norman and given fire by Jesse James Garrett's book, Elements of UX.
It was never intended to be a role, but rather an approach and possible a department. But the best intentions… UX Designers coined themselves, and it often meant IA+IxD+ UI but not Visual Design. So flow → wireframe and no more.
But again, sloppy titles led to sloppy definitions, and soon it picked up visual design and front end coding, and bit of design research. People with these skills sets were perfect for startups, the meant and potatoes of Silicon Valley.
So the education startups, General Assembly, Tradecraft et al, started pumping them out. Visual designers, marketeers, architects and former Trader Joe’s managers took a two month boot camp and hung out their shingle: UX Design done here.
The rise of the product designer is a mystery to me, but I have two theories.
1. The weakening of the value of the title UX Designer
2. The realization that UX really is too big for one person, but IA+IxD+ Ui is “just right.”
Together, I think this iswhy we see the shift.