It's really important to understand that puberty is not just about sexual development. It matures the whole body: brain, bones, liver etc.
There is a window of opportunity to go through puberty in your teens. If you start taking PBs and stop during that window, you should go through puberty without problems so, in that sense, they are reversible.
However, if you take them past the "puberty window" and then go straight onto hormones for the opposite sex, you will never go through puberty. Taking high levels oestrogen & progesterone (or T for TIFs) will to some extent mimic the superficial effects of puberty - so TIFs will grow facial hair and TIMs will develop breasts. But this is not the same as normal puberty. These sex hormones actually suppress the brain's production of the hormones that drive puberty.
So PBs then hormones past the "puberty window" will leave people perpetually immature in their physical & brain development. The closest parallel prior to the trans madness were the castrati - the boy singers whose testicles were removed, so they never went through puberty. They had numerous health problems; here's one description:
As the bodies of a castrato grew, a lack of testosterone restricted his bone joints from hardening in the normal way. The limbs of a castrato often grew unusually long, giving them a seraphic look.... Their physical appearances and unique voices made them stick out
But while the form of the castrato was seen as elegant, the repercussions of the surgery were often felt later in life when their large bones developed osteoporosis and their organs began to struggle beneath the weight of their extremely tall bodies. It was also common for castrati to become depressed as they aged. Many felt extreme mental anguish, were extremely sensitive, and often had an erratic mental state. Researchers aren't sure why exactly, but research of castrati bones show the many of the singers developed hypertosis frontalis interna. The rare disease occurs when the front bone of the skull thickens, and causes seizures, headaches, and affects the sex glands
This is the future for trans kids 