Not sure if this is a bug or not, but I don't see why it wouldn't be.
Ok, you summon a flesh golem, it dies, you can summon another from it's corpse - right? Ok then.
Summon a flesh golem, a random monster dies and you summon another flesh golem to kill the first and start a new one (low health, low level - whatever). This uses the random monsters corpse, but it ALSO exploits your previous flesh golem's corpse as well. So instead of, say, being able to summon another fiend or something from my golem's corpse, this effectively exploits two corpses in one shot.