When riding a horse you are unable to see the exhaustion bar and saturation overlay from apple skin.

This mod fixes this problem, but I feel it would be appropriate for Horseman to have support natively.
https://www.curseforge.com/minecraft/mc-mods/leave-my-bars-alone

Mount GUI stuff is a fragile feature, changing one thing can break another.
And judging by Leave My Bars Alone class AppleSkinIntegration, there's some intricate code needed to make it work (at least on 1.20.1).

So I'd rather not touch it for a minor issue like this. My recomendation would be to just disable Horseman feature and use Leave My Bars Alone in this case.

Mount GUI stuff is a fragile feature, changing one thing can break another. And judging by Leave My Bars Alone class AppleSkinIntegration, there's some intricate code needed to make it work (at least on 1.20.1).

So I'd rather not touch it for a minor issue like this. My recomendation would be to just disable Horseman feature and use Leave My Bars Alone in this case.

Why instead of fixing ANY issue you keep saying disable and use another mod

The mod is open source, you can help fix the issue by creating a pull request.