Not technically true. Puberty blockers have been used for a while by endocrinologists to help delay puberty, and the resulting fusing of the growth plates. Generally prescribed in short stature scenarios in conjunction with growth hormones (if deficient).
However, the medically prescribed usage of the blockers have been hijacked by gender ideology.
After you go through puberty the result isn’t reversible. But delaying puberty for a year or two is in general possible—and stopping the blockers will allow the puberty process to take hold. Now, if you delay puberty and flood the body with with synthetic T or E, opposed to what the body would produce—THAT is irreversible.
Oh absolutely