Ladder effect of scaffolding only works if the center of the player is in it

The bug

When the center of the player is not above scaffolding, they are not experiencing its ladder effect: Smoothly going up and down.

Instead they jump up one scaffolding block at a time and fall down multiple scaffolding blocks when going down.

This is related to MC-1133, but possibly not a duplicate, because some functionality (that you can go up and down) works as expected.

How to reproduce

1. Build a tower of scaffolding
2. Move partially inside it, but make sure that your center is not inside it
3. Move upwards by pressing the jump key
   → You jump up one block at a time instead of going upwards smoothly
4. Move downwards by pressing the sneak key
   → You fall downwards