Puberty blockers are not fully reversible. It isn't like someone hits a pause button on puberty, as much as people like to portray it that way. I Am Jazz even displayed one of the consequences -- Jazz had inadequate penile growth, and thus wasn't really eligible for the more common and preferred vaginoplasty. And you're definitely messing with height, as any surge in estrogen can cause the growth plates to fuse -- completely non-reversible, to the dismay of all kinds of people.

Time marches on in the human body, whether we like it or not. Now, show me a "perma-kitten," a cat developmentally frozen in full kittenhood, behaviorally and all (something I think would be immensely popular with some crowds) and then undo it, only then will you be close to this pause button which puberty blockers cannot well emulate.