At least post-Pig, the Dead were in no way a true blues band.
I personally also never found them able to convincingly cover any of Chuck Berry (especially, I hear none of Chuck's special swing in their versions).
But it's still the Dead.
I wonder if you actually listened first to the segment of the video I posted with Jerry on slide. If not consider giving the video, starting at 15:10, a brief try. (In my first post, I said start at 14:40 - that's when the song begins with Bob on slide - but Jerry picks up the slide at 15:10).
I play slide myself. With my current band, for example, on our ABB covers, I handle Duane's parts.
I'm in no way an excellent slide player (yet) - adequate would be more accurate - but I know enough to know one when I hear him.
Jerry's slide on the LRR version I shared is really nice.