Naturally spawning Villagers do not have correct skins

I originally had this bug as of 19w05a.
It has not been patched since.

Upon generation, Villagers will spawn with unique "clothing" to fit their biome. This is not the case. All Villagers I have found, after countless new worlds, all have the default "Plains" skin.

Attached is a screenshot of a Villager in a Tundra Village, with the Plains skin.