Cows and horses only spawn in unexplored chunks once

Cows and Horses only Spawn in a unexplored chunk once but pigs, sheeps and chickens Spawn in a unexplored and explored chunk

Steps to Reproduce:

​Create a new Survival world in Java Edition.

​Explore chunks to let initial mob generation happen.

​Kill or clear passive mobs in those already explored chunks.

​Wait for passive mob respawns in the explored chunks over time.

​Observed Results:

Only pigs, sheep, and chickens spawn in the already explored chunks. Cows and horses do not spawn there anymore and can only be found when entering newly generated (unexplored) chunks.

​Expected Results:

All passive farm mobs, including cows and horses, should have a chance to spawn during passive mob respawn cycles in explored chunks (provided valid biome conditions are met).