Wooden Trapdoor stays after supporting block is broken

While playing the current snapshot, I noticed after breaking the dirt blocks supporting a few wooden trapdoors that the trapdoors did not break. Usually, a trapdoor or door will destroy itself and turn into an item after its support is broken. I wanted to report this in case it was not a planned change, as it surprised me and seemed to be a bug.

Attached are a few screenshots showing the floating trapdoors and that they can be opened and closed without breaking, meaning that even a block update won't set them off.

Hope that this helps,
-Tadd