The bug
Mobs summoned with no health (Health:0f) will not drop any loot.
I expected that mobs summoned this way drop loot.
Steps to reproduce
Summon a mob with Health:0f in their NBT tag
/summon zombie ~ ~ ~ {Health:0f}
For comparison summoning a mob with health then killing it will drop loot
/summon zombie ~ ~ ~ {Health:1f}