>>39008379With the assumption they will be added again incrementally in later games after this and they're wiping the slate clean as far as availability goes just to sell more down the line, then they only need enough to provide variety of types and meet the numbers of the first few games. Throw in the assumption they only add maybe 20 new pokemon total and they could wipe all but 130 and be fine for these games and then release more games faster and sooner with less need for new designs as it would be "unlocking" old ones.
This is far easier and cheaper than remaking entire old games like they did before.