A lot of quotations in the article get the SCOTUS ruling wrong, sometimes completely backwards.
The emergency order wasn't anti-trans (that issue wasn't on the table at all) but rather pro-freedom of speech. They were 1st Amendment concerns at issue in the argument.
And so, the article says schools can mandate the outing of trans students, but by the same argument schools would be prevented from exactly that.
Maybe advocates do fear SCOTUS is going after the trans community. If they do, then they don't understand the law. Or maybe they're just stunting for political points.