Multiblock items like beds and doors,(all i've tried so far) will drop 2 of themselves when broken from 1 specific portion. If i break a bed from the bottom half it drops 1 but if i target the pillow it drops 2. Doors its the bottom half that duplicates the door. It has been 100% repeatable at least on our 1.16 pre4 server. Works in single player as well as in creative.