Falling into powder snow does not prevent fall damage when falling certain distances

I have been testing out the powder snow with fall damage. I found that one block of powder snow at Y level 66 removes all fall damage.

To reproduce

1. Place a powder snow block at Y: 66
2. Place a platform at Y: 62
3. Fell without any armour from Y: 164
   → Your fall damage is reduced
4. Fall from Y: 165 or Y:163
   → You die