I am the developer for Bumblezone and I got this bug report:
TelepathicGrunt/Bumblezone#528

The thing is, my mod's chestplate has no sleeves so I would expect the I See My Armored Hand mod to render the player hand and I not need to call any API for rendering

Instead, the user is reporting that I See My Armored Hand mod is just not rendering the hand properly when my armor is on.

With wearing my chestplate but without the I See My Armored Hand mod

With wearing my chestplate and with the I See My Armored Hand mod

I do not see why I See My Armored Hand mod cannot render the player hand by default and then the API for rendering would be for rendering the armor on top of the hand rendering. There's no reason for me to call the API just to render the player hand myself for my sleeveless chestplate.

I'm testing a new implementation for 1.21.9+ in which all mods and resource packs should be compatible. If it works correctly, I'll try to backport to previous versions.