Description:
Using a water bucket while aiming at an upper slab places the water at a high of a bottom slab. Water appears a block lower than it should.
Steps to recreate:
For ease of reproduction, place a full block on the ground.
Place an upper slab on the side of the block.
Aim at the top side of the slab.
Use a water bucket.
Observe the result.
Observed result:
Water source block appears beneath the slab despite using the water bucket on top of the slab.
Expected result:
Water source block appears on top of the slab after using the water bucket on top of the slab.
Attachment: A video comparing where water and lava appears after using buckets filled with corresponding liquids on top of an upper slab.
Sneak.This is behavior that applies to ALL waterlogable blocks and by design.