It’s absolutely true based on every EMT I’ve spoken to. Which, by the way, I highly recommend if you have the opportunity and the stomach for it. They have some wild stories to tell.

Indeed. I'm an EMT and because of cases like this we're taught not to assume a cold or drowned patient is dead until they're warm and dead.

Not for nothing, with children there is often a greater “spirit not to give up.”

That's true, but there's also a hypothesis that kids freeze quicker because of their lower body mass, which may make them shut down more uniformly with less damage. Which means thawing them out has a better chance of success.