The motor is a few years older than the buggy, but i don't think that means it isn't period correct. Joel Johnson's championship winninng Ultima uses Futaba G plug Rx, ESC, and steering servo. In 1987 the new hardware would have been Futaba J plug, but he apparently used some existing electronics. There would have been plenty of those Twister motors still in use in 1996.
If a new in 1996 motor were used, it would probably be something with laydown brushes. I think that's when they were popping up in things like the Trinity X-Star stock.