Blaze Rod drop error?

Out of boredom I wanted to use an iron golem to kill blazes since golems can kill zombie, skeletons, pigman, and other mobs to drop items, so I decided why not use them to earn the blaze rods? one thing I learned is that for some reason blaze rods don't drop when they're killed by an iron golem, along with this I tested 100 blazes and drowning blazes dont drop their items aswell....