Yes it's emitted from the sun, it's clear given that the time-lapse shows "Inner moon eclipsed" when passing behind the site of the asteroid that is not lit.
But, you have pointed out something interesting and that would appear to indicate other wise. The clear rotation independent of source already shows that I am wrong on that.
Apparently I don't understand this very well.
They do all sorts of fancy signal processing to get this sort of resolution.
Because radar power received goes down with 1/(distance^4), the inverse square law, squared, this is hard to do at astronomical distances.
The power level differential between transmitted and received power can be in the order of ~10^15.
Goldstone transmits a 500kW radio pulse but will probably get nanowatts back, which is amplified millions of times by the big dish, amplifiers and signal processing.
There are two things: the radar images are created with radio waves emitted by the radar installation. The second thing is that the visualisation shows a light source. They are unrelated to each other. I assume that the light source was added during rendering of the film and that it approximates the sun.
The actual solar illumination of the asteroid at the time was likely significantly different from what we see in these images.