Arendelle was already evacuated. No people were in danger from the tidal wave. Elsa was just saving the city from physical destruction.

I think you can also make a converse argument to the author very easily: death and disaster are common, almost universal, so avoiding discussing them in children’s media is over-protective.

In any event, I think there’s a point being missed here: the ratings system is a self-regulatory measure and mostly represents a way to classify films as the culture as a whole views profanity. In that respect, they have shifted over time as the definition of “acceptable” has shifted over time.

The author is really just lamenting the fact that their views don’t line up with the majority of Western society.

And that’s perfectly okay because the MPAA rating system is just one voluntary rating system of many. Parents are free to entirely ignore it, or they can reference the information rating systems from other countries, or third parties like common sense media.

As an analogy, the author could be upset if they were from a majority Muslim country and then decided to visit a nude beach in France. They might be upset about public display of nudity in that context. But they are in France and that is what is culturally acceptable in France in that specific public space.

Children’s fiction has always had a very dark side though.