>>48610359200 pokemon is about the smallest you can make a dex while still covering all your major bases (multiple methods of finding pokemon, type diversity, varied pokemon distributions, etc.). Anything smaller than that will require some concessions on the developers' part, and removing 50 pokemon from that number (roughly 25 families) effectively ensures that at least one of the aforementioned bases will have to be neglected:
>Kanto limited most new pokemon to dungeons, strategically placed single-stage mons to cover for type shortages, and kept ghost and dragon types to a single line (not having to worry about dark or steel types also helped)>Unova heavily simplified surfing distributions, gutted fishing from the campaign, and avoided any 'hyper-diverse' distributions like Kanto's Safari Zone to give all areas roughly equal numbers of new pokemonSinnoh's dex had to meet these same challenges as well, but several of its design decisions forced it into an even smaller box than its predecessors:
>Had to include 'legacy' mons (abra line, zubat line, etc.), constraining the mutable size of the dex to around 120>Honey trees meant an excess of bug types localized to a place most players wouldn't think to spend much time in>Fishing meant an excess of water types in one of the driest games in the seriesSinnoh's dex also has a lot more emphasis on 'overlooked' types than the rest of the series (4 ghost types in a single region?!), which further reduces the number of available pokemon for other types.
What confuses me is why GF didn't play to the region's strengths instead of its weaknesses. Sinnoh has a massive number of Poison and Normal types compared to other dexes, but for whatever reason they decided to make two of the game's key bosses Fire and Electric specialists instead. Platinum ultimately resolved most of these issues anyway, but it makes me wonder how much cross-talk there was between the people designing the dex and the people developing trainers.
