You're missing the forest for the trees. The underlying point is that serious for-real consequences; beyond a slap on the wrist but tangible, real, do not buy your way out of jail consequences need to happen.

Would you feel better had he said "sent to get shived in the shower prison"? The meaning would be the same.

Or is it simply any kind of real description of what prison is like that you object to?

It indeed is and points to serious problems in the criminal justice system that destroy the argument of whoever is using it as a threat