Rails on top half trapdoors do not break if the trapdoor below them opens

The bug

If a rail is placed above a top half trapdoor and then the trapdoor is opened, the rail does not break until it receives a block update. This is not the case for ladders against open trapdoors when that trapdoor closes.

Credits

Special thanks to [Mod] tryashtar in this video for discovering that rails can be placed on top half trapdoors.

How to reproduce

1. Place a top half trapdoor and then a rail above it.
2. Open the trapdoor below the rail.
   → The rail does not break.
3. Update a block near the rail.
   → The rail breaks.