Well… to be honest I kinda feel like that’s just reading way too much into it… and it’s also probably worth noting that there are no three-stage Electric-types in generation one (although whether that would necessarily have mattered in the formative stages of the game is hard to say)… but… oh, what the hell, let’s go look at the damn hex numbers and see if that says anything.
(Obligatory explanation for anyone reading this who doesn’t know what these are: every Pokémon has a unique hexadecimal (base-16) number that identifies it within the games’ coding; from Ruby and Sapphire onward these ID numbers follow Pokédex order, but in the games from the first two generations they’re all over the place, and we think they represent the order in which Pokémon were created, since Rhydon is 01 and we know independently that he was the first design ever. It’s therefore possible – if you’re sufficiently credulous – to mine this list for patterns that tell us things about the design process of the original Pokémon games.)
So, I’m pretty sure the establishment of Grass/Water/Fire as the standard starter trio actually did happen very late. This is because Squirtle, Wartortle, Charmander, Charmeleon and Charizard turn up all together at B0 to B4, near the very end of the list, and I think this represents the moment they decided on a selection of three three-stage starters. Bulbasaur and Venusaur come in a little while before that; Ivysaur and Blastoise have both been around for ages by this point. So, on the one hand, there is good reason for thinking that the mechanism by which players received their first Pokémon was fluid for a long time during the game’s development, but on the other hand it’s the Fire and Water starters who are late to the party, not the Grass-type. It’s sort of difficult to come up with anything more solid than that… although you can, I suppose, look for places in the list where Grass, Water and Fire types seem like they could have been designed all together – there aren’t any – or for places where Water, Fire and Electric types seem like they could have been designed all together… and there are, interestingly, two of those. One is the set of Pikachu, Vulpix, and a Pokémon that was actually rejected from Red and Blue but ultimately resurfaced in Gold and Silver as Remoraid (EDIT: take this with a grain of salt – see comments section). The other… the other is Eevee and her evolutions, and Eevee’s role in Yellow Version does make it awfully tempting to suggest that maybe she was intended as the starter Pokémon up until Charmander and Squirtle were designed. Total conjecture, of course. Can’t prove a word of it. But it’s interesting to speculate.
Pokémaniacal 