>>44823686I'm not that anon but I am the creator of the image. I created those teams for a Pixelmon adventure map and that pic is outdated.
If you want a better idea of how it would work in practice, the 6th team would really be used for the 7th badge, too with movesets being the major difference between them with maybe an evo depending on the leader.
That version has got to be pretty old considering it's got Graveler as the "8th" battle. Good eye on the rematch team thing, though. Because "8" in that image is supposed to refer to the rematches, not the actual 8th badge. As for the number of pokes/level, keep in mind HGSS bumped up the levels of the Kanto leaders significantly. In GSC, Brock's Pokemon were all in the low 40s and for some reason GF decided not to evolve his rhyhorn until the rematch.
In context of the Pixelmon map, though... Gym leaders levels scale to the highest level the player has. So it's supposed to be more based on strategy and moveset rather than pure grinding. Interesting to see the pic posted in this thread, though.