In my opinion, the tag signifies original content that matches the art style of the show. I interpret that as not applying to screencap vectors, because the inherent point of doing so is to reproduce the show’s own content (offering higher fidelity) - a skilled craft, but not involving the artistic decision that “show accurate” is meant to highlight.
This is just my view - hopefully more people will chime in, or an assistant could point to an official definition somewhere.
P.S. Also IMO, I see a number of pictures tagged as “show accurate” that, subjectively, I wouldn’t judge as being so…