From Ver.1.20.60, horses will now receive fall damage while riding...

This is intentional per the changelog:

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

https://feedback.minecraft.net/hc/en-us/articles/23875745708557-Minecraft-1-20-60-Bedrock

disappointing…
voting site「URL→https://feedback.minecraft.net/hc/en-us/community/posts/23959961167757-I-want-to-add-fall-reduction-to-horse-armor←」