Iron door drops without using pickaxe if you break the top half

In survival mode, iron doors should only drop the iron door item when mined with a pickaxe. However, if you mine the top half of the door using bare hands or any item, then it drops the iron door item.

Steps to reproduce

1. Place an iron door.

2. In survival mode, mine the top half of the door with an non-pickaxe item until the door breaks.

Expected result

Nothing drops.

Actual result

An iron door item drops.

Demo: https://youtu.be/27CpI3ngkbs?t=62