If you're in the camp who treats UX as a professional title/career, then in principle it has very little to do with UI, and being labelled "UX/UI" is often an "insult" to UX professionals along the same lines as "Computer Scientist / IT support", or "Electrical Engineer/Electrician", "Civil Engineer/Sanitation Engineer", "Pharmacist/Teller at Boots", "Doctor/Medical receptionist". (not to imply that the latter professions are 'lesser', but rather to point out that the former professions in the pairs are typically deemed to require a higher standard of skills/training rather than simply vocational/apprentice-based training).
At the same time, I'm not naive to not understand the fact that, if a large number of people start referring to X as Y, then after a while, insisting that X isn't Y is a lost cause, and you might as well start calling it Z instead.
But, e.g. my wife was a senior UX professional who is now doing her PhD in Experimental Psychology; the original motivation was that this would make her a better UX researcher when conducting controlled experimental studies on behalf of her employer. She specialises in voice assistive tech, and her topic relates to isolating auditory markers of voice trustworthiness. I can tell you if she applied for a UX job and the interviewers started asking her what css colours she prefers on buttons, she'd be pretty pissed.