Hostile mobs do not drop any drops (except for armour for skeletons & zombies) when killed, either by natural (fall damage, fire, drowning, ect) or by the player in creative. In survival hostile mobs will drop drops when killed by player, with a bow or sword, but through "natural means" like my mob grinder, they do not drop anything except for armour.
MCPE-11689
Hostile mobs do not drop their drops
Resolved
Fixed
2
(Unassigned)
Confirmed
Tablet - iOS - iPod Touch 5
iOS 8.0
0.13.0
0.14.0 Beta 4
Retrieved
Confirmed on Samsung Galaxy S4 Active, Android 5.01 MCPE 0.13.0 single player creative, spawned zombies and chickens from eggs, killed with a diamond sword. Only the chickens dropped items.