Worth noting that puberty blockers have other medical uses for children aside from care for trans (or potentially trans) individuals. For example, precocious puberty can have some pretty heavy negative health effects in young children, and the primary treatment is puberty blocking hormones.
Point being, we already treat children with some other medical conditions with puberty blockers. If medical professionals and researchers have found that they're also the treatment with generally the best outcome for people with severe gender dysphoria, it seems ridiculous to me to try to deny them that care by law.