The bug
While water has six faces which it renders on the outside, only five of them have equivalent inside faces. The sixth face (the bottom) will never render from above/inside of the water block.
Note that the provided screenshots do not show side faces for water either in most cases - this is a result of MCPE-34085 (a ticket which should also be given the fluid-geometry and missing-planes labels). Unlike that ticket, the bottom face is not nonexistent due to any underlying blocks, as can be seen by breaking the pressure plate in the setup and noting that for the instant in which no block is below the water, there is also no bottom plane.
How to reproduce
Create the setup shown in the screenshots
Enter the water block
Expected results
The bottom face of the water would be visible.
Actual results
It is not.
How to fix
When Bedrock Edition finally gets block models, it should get fluid models as well - planes could be defined for these faces such that they actually exist.
I can confirm. However, the report does not reproduce the problem, since all blocks in the bedrock (including incomplete ones remove the sides of the water). For playback, I would recommend just placing a water block in the air (/setblock ~ ~ ~ water). In this case, only the lower side will really be missing from the water.
Changed:
Same with lava!
[media]Place lava in the air with a command /setblock ~ ~ ~ lava.
Get the effect of fire resistance.
Go inside the placed lava block.