Quality of it is completely separate matter and doesn't change the fact that "DLSS 4k" is not 4k while sounding close enough to fool most not tech-savvy people.
Calling it DLSS 4K isn't a deceptive marketing term unless you advertise the performance with DLSS enabled without mentioning DLSS being used as being better than the competitor that does not have DLSS.
The above is assuming you
could tell the difference objectively through the use of comparing screenshots of DLSS 4K having inferior quality to a native 4K image.
Having said that, if Nvidia gets DLSS to a point where you
could not tell the difference in quality between a 1440p and a 4K screenshot, even when zoomed in , then is it really fooling not tech-savvy people or really anyone if you used DLSS 4K and 4K interchangeably?
Side note: If you randomly added DLSS to the beginning of something most people would ask what that meant.
Aquafina DLSS Pure Water (I'd ask a lot of questions before drinking lol)
Chevrolet DLSS Camaro
DLSS BLT