Issue:
When walking from a top trapdoor onto a scaffolding block the player just falls right through the scaffolding as if it wasn’t there. This happens with all trapdoors, including iron.

Expectation:
Walking from trapdoor to scaffolding behaves like every other exactly full height block. Allowing the player to freely walk onto the scaffolding.

Recreate:
1. Place a top trapdoor.
2. Place scaffolding next to the trapdoor.
3. Walk off the trapdoor onto the scaffolding.
4. Observe that you phase right through the scaffolding.

Fixed in 1.16.0.