You know… it used to be the case that when using an acronym in an article, it was always explained after the first usage in the text. Journalistic editorial standards have really slipped.
It's not an acronym anymore. It used to stand for Parents and Families of Lesbians and Gays but they have expanded their charter to include all their members. Since it's not an acronym, and hasn't been for about a decade, I assume they decided to to bother to explain what it used to stand for since it's not relevant to the article.
In 2014, the organization officially changed its name from “Parents, Families, and Friends of Lesbians and Gays” to, simply, PFLAG. This change was made to accurately reflect PFLAG members, those PFLAG serves, and the inclusive work PFLAG has been doing for decades.
I assume you're talking about not defining PFLAG? Acronyms widely understood by the target audience aren't always defined. The LA Blade is an LGBTQ publication so PFLAG not being defined makes sense.