A Conspicuously Singular “They”

Many writers use “they” as a singular, particularly when they don’t know or they want to conceal the gender of whom or what they are referring to. Writers have done this for a long time (centuries) and sometimes it feels natural, even, but this example jumped out at me:

Authorities have arrested an individual who is allegedly part of The Chuckling Squad, the hacker group that compromised the Twitter CEO’s account in August, according to Vice. The alleged member was arrested around two weeks ago, but isn’t named because they are a minor. 

https://www.vice.com/en_us/article/gyzawx/authorities-arrest-suspected-jack-dorsey-hacker

(I should add that the quote is from a summary on the Recode Daily website, though the usage occurs in a similar sentence in the original (linked) article.