Sneaking on climbable blocks when being on the ground counts as not being on the ground

The Bug:

When sneaking while standing on the ground and on a climbable block you are not considered to be on the ground. This causes you to mine blocks slower and not be able to do sweeping attacks. You also will not get upward knockback. Scaffolding is not affected by this bug.

Steps to Reproduce:

1. Place a ladder on the side of a block.
2. Go into the ladder but remain on the ground.
3. Put yourself into survival mode.
4. Mine any block.
   The block will be mined slower as if you were in midair.

You can also put these two commands into two repeating command blocks to know whether you are considered to be on the ground or not:

1. title @a[nbt={OnGround:1b}] actionbar {"text":"On Ground"}

2. title @a[nbt={OnGround:0b}] actionbar {"text":"Midair"}