Slab breaking takes as long as to break their full-block variants

When in survival mode (gamemode 0), it takes the same amount of time to break a full block as a half block. This does not make any sense at all! Why would you need to punch as much to break literally half of the block as for the block in full?

How to create:

1. Acquire any block with their respective slabvariant

2. Go into survival mode

3. Break first the full block, then the slab

(It might be a feature though, but needs clarification)