>>56919024GSC's Kanto was neutered. And HGSS's Kanto was more like the 2nd half of the game than a bonus postgame.
Compare the overworld design of RBY/GSC with the visual involvement of RSE's maps. FRLG/HGSS's maps needed more than a new coat of paint. You run right through them that it's kind of expected to have the Kanto half.