Obviously, but the kind of UX discussed here is obviously that of graphical applications; nobody would say that a web API's or a compiler's UX is a "stuttering mess".

Basically everything computer that interfaces with humans is graphical. That doesn't mean it's in the designers domain to fix.

A designer is not responsible for making sure that the implementation of their design runs at stutter free at 60fps in a browser -- that is an engineers job. If the engineer who implements such a design is insensitive to these things and needs convincing that it's important to not have the implementation not stutter, jerk or jank you are never gonna get good results.