>>57403366they did want you to use the new type, but they only wanted you to use Umbreon because it's a designated shillmon.
Murkrow and Houndour were used by Team Rocket so they're too "evil" for the player, hence being banished to Kanto, and Sneasel is used by the rival, who's an asshole, and the player doesn't want to be an asshole, so they banished Sneasel to the final area of the game. And Larvitar's the game's ultimate secret, thus it needs to be hidden in the final area of the game and no NPCs use any members of its line.