As ghastly as the whole story is, it's the unexpected failure mode that seals it as a metaphor: Another serious training mistake was revealed later; the Soviet

As ghastly as the whole story is, it's the unexpected failure mode that seals it as a metaphor: Another serious training mistake was revealed later; the Soviets used their own diesel engine tanks to train the dogs rather than German tanks which had gasoline engines. As the dogs relied on their acute sense of smell, the dogs sought out familiar Soviet tanks instead of strange-smelling German tanks.