The idea is that the blob has some limits on exactly how much damage it can repair for a broken corpse. Pass those damage limits, and the bit of blob inside the corpse just dies rather then being able to successfully reanimate the corpse.
So when you are smashing them you aren’t so much “making it harmless”, as just accumulating corpse damage until it’s a fair ways past that invisible “threshold” (and is thus why they don’t revive and just get stuck twitching in place).
Hypothetically the blob should be able to repair an infinite amount of damage to keep standing up if given enough time, but at no point can the damage exceed a given threshold or it just ends that particular zed permanently.