help me understand where the logic in this?
I don't know.
You don't really provide any meaningful information.
Based on the OP a judge one day decreed getting a vasectomy or implant gives you 30 days off your sentence.
There are states, like CA, that can force chemical castration.
At least this, according to the little information in the OP, is voluntary.
Maybe that's the logic? "If you're willing to volunteer for a vasectomy or willing to be implanted with birth control (which may or may not reduce sexual urges, in repeat sex offenders?) then you are showing that you are in a sense repentant for your crimes and working to avoid recidivism."
Do you agree with snip, snip the family jewels will be beneficial?
Maybe.
For all I know the judge allows a 30 day credit only to those serving 70 years, or repeat sex offenders.
For all I know the judge is 102 years old and going senile and thinks the humors in the genitals are leading to criminal behavior.
just a crazier way of depopulation our country?
Do the inmates in question already have kids?
Are they sex offenders?
Do the female inmates in prison keep getting knocked up and the babies are born in prison creating a huge burden to the system?
Can't really explain the logic or see it as a crazy way of depopulation our country without more meaningful information.