Ladder trapdoor climbing is hardcoded and cannot be influenced using 'climbable' block tag

The bug

A trapdoor with a ladder below is considered climbable. This is hardcoded and cannot be influenced using the climbable block tag.

See also MC-129299

How to reproduce

1. Download the attached datapack MC-174100.zip which removes ladders from the list of climbable blocks
2. Place a trapdoor with a ladder below, both attached on the same side
3. Open the trapdoor and try to climb it
   You can climb on the trapdoor

Code analysis

20w10a, Mojang names

Ladders are hardcoded in net.minecraft.world.entity.LivingEntity.trapdoorUsableAsLadder(BlockPos, BlockState)