I had been wondering for a while about what was special about the dead coral fan in Minecraft that allowed it to be used for TNT duping. The answer is enlightening:
The coral is unique in that it behaves like a block that breaks when slime it's attached to is pushed (like buttons, torches, and so on) playing the breaking animation and sending updates like any broken block, but does not actually break - continues to be affixed to the slime, pushed by it so it can pretend to break in the next cycle.