^{Update by myself:}
Steps to Reproduce:

1. Place a top slab floating in the air;
2. Surround it with top slabs so the water doesn't flow sideways;
3. Waterlog it and let it flow downwards.

Observed Results:
By looking at the waterlogged slab, it can be observed that the back sides of the water are invisible, which is inconsistent with the water that's directly beneath it.

Expected Results:
The water texture is displayed on all sides when it's surrounded by non full blocks.

Screenshots/Videos attached: Yes

Notes:

Original Description:

When I put water on an upside slab, it shows the water properly from the outside, but looking from the inside, the it doesn't show the water on the slab.

If I haven't explained very well, just look at the images and you'll know what I'm talking about.