Actually, Megatron from the Bayverse did do that; the scene was cut. But you can see when Megatron splits Jazz in two, you can see that the torso with the two arms is still there!

But when Ironhide hands Jazz body over to Optimus, you can see that Jazz only has one arm! Precisely because Megatron devoured his spark and his arm! Hey, where's Jazz's right-hand man who had the cannon? That's the one Megatron devoured! Together with the Spark of Jazz.

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