Players are breaking blocks despite being in a 1x1x1 hole

I was trying to exit my secret base by swimming into a 1x1x1 air gap and when I tap the trapdoor, the trapdoor didn't open nor close. Instead, I am able to break blocks outside of the trapdoor. That would make my secret door essentially unusable.

What I expected to happen was...:
The trapdoor should respond when I tap by closing or opening.

What actually happened was...:
Instead, it did not respond. But I am able to break blocks outside of the trapdoor. This works with an iron trapdoor.

Steps to Reproduce:

1. Build a pool of water (I'll provide a screenshot)
2. Place a trapdoor at the corner (just like the screenshot)
3. Swim towards the trapdoor and quickly open and close the trapdoor to enter the trapdoor'S beneath (I might make a clip)
4. Try tapping the trapdoor. Nothing will happen. Instead, you will be able to break blocks outside of the trapdoor. This would be annoying if it is an iron trapdoor.

Evidence: https://streamable.com/fx2lc