Op said that teenagers are by definition children, not that they are by a definition children.

Sure, you can use the term more broadly, no sense to deny that. I suppose that my argument is that then most common understanding of the word would be to use 'children' to describe a prepubescent person.

You are not wrong to point at me tough:

In English-speaking countries, the legal definition of child generally refers to a minor, in this case as a person younger than the local age of majority (there are exceptions such as, for example, the consumption and purchase of alcoholic beverages even after said age of majority[6]), regardless of their physical, mental and sexual development as biological adults.

https://en.wikipedia.org/wiki/Child

I personally think it is mudding the waters to use a legal definition without making this clear. 'Trump raped a child' evokes a different idea than 'Trump raped a teenager'. Than again, in this specific case both definitions of child would very likely be true.