https://apastyle.apa.org/style-grammar-guidelines/grammar/singular-they/
“Both “themselves” and “themself” are acceptable as reflexive singular pronouns; however, “themselves” is currently the more common usage”
APA is the accepted English for scientific papers and what we grade for at university at least in the American side of the pond.
The author specificity says they don’t normally report on suicides. This is to avoid the glorification / notoriety effect that could encourage copy cats. You can tell they specifically are being vague with information towards that end. I wouldn’t read too much into the “themselves” thing. Being a minor there won’t be more info released unless the family releases it.
Except that here, it’s not so much the word, “themself / themselves” (although it’s marginally bad). It’s the “s” at the end. It makes it a plural when the subject is singular. There’s no agreement.