When their block state changes, waterlogged blocks don't remove water they let through

The bug

When their block state changes, waterlogged blocks don't remove the water they let through, even though that water logically should not be there anymore. The water then only disappears after another block update.

To reproduce

1. Build 2018-03-09_20.36.01.png (notice that the trap door itself is waterlogged, and is attached to the right side of the left block, not to the left side of the middle block)
2. Right-click onto the trap door
3. Wait a moment
4. Right-click onto the trap door again
5. Wait a moment
6. The water does not disappear
7. Use the button
8. The water disappears

It is also possible to reproduce this bug using stairs, see Minecraft 18w10d 2018-03-09 17_16_44.mp4