I've been reading a lot of Pokehistory lately, so let me help you.
A Pokemon's national or regional dex number does not have to do with when it was created. This was, however, the way they had originally planned it to be, which would have made Rhydon #001 and put Victreebel at the end of the pokedex. If you want to show your friend something, I learned this from a YouTube video from user "dykgaming" entitled "Pokemon- Did You Know Gaming". I'm not entirely sure, but from my own experience I can guess that the pokedex is arranged in the order you encounter them.
Also, for more proof, you can search "Capsule Monsters" on Bulbapedia and you'll see that Rhydon is one of the Pokemon in the concept sketches (along with Gengar and Nidorino). These Pokemon would be first in the pokedex if it was arranged that way.
I hope this helps!