Minecraft v1.16.4
Forge v35.1.13
More Waterlogging v1.4

If a door is placed so that only the bottom half is in the water, the top half will still become waterlogged. If the door is broken by hitting the top, the water source at the bottom is deleted.

I tried placing the door with version 1.5 of the mod and I can confirm that it still does happen.

At least, the water still appearing in top half when placing the door in 1 block deep water.

does this still happen in 1.5?

I'll give it a try soon