Mob Spawner in Mooshroom Biome affects the entire Biome, and mobs spawn as if in another mob-supportive biome.

This is not a duplicate of MC-61966! I believe he wasn't descriptive enough.

When I enter a spawner on a Mooshroom Biome, (totally unlit in every cave and cavern)...every cave, cavern, surface area etc comes alive in the mooshroom biome with zombies. Its as if the spawner turns on spawning in the entire biome. If someone is 40 or more blocks away, but still on the Mooshroom Biome, zombies will spawn near him too. We confirmed that they spawn in Mooshroom Biome blocks.