Puberty blockers have been used for decades to treat various conditions including to delay puberty in very young children who aren't ready for it developmentally. Whether the drugs have ever been used in circumstances you're asking about, I don't know. I do know that taking them can be life saving for trans kids, and that the decisions are best left to families and trained physicians, who follow standards of care that have been carefully thought out by professional associations and regulatory bodies.

The Endocrine Society and the US board governing pediatric medicine both approve prescribing puberty blockers in trans children under certain conditions.

The trouble here is that an attorney general with no medical training is overriding two boards of physicians who actually know what they're doing.