As the 1.20.60.21 changelog said:

Horses, Donkeys, and Mules now take fall damage when controlled by a player, except for worlds targeting base game versions before 1.20.60 (MCPE-107031)

After these fixes horses got damage but player while controlling don’t take damage. This mechanic was used before horse immune damage bug came.

Steps to Reproduce:

1. Go to the edge of mountain or hill while riding horse, donkey, mule, or camel
2. Now ridng straight for falling to the land

Observed Results:

Horses or camel take damage but player doesn’t

Expected Results:

Both of them taking damage