Prisoners in open jails do not have complete freedom and are only allowed to leave the premises for specific purposes, such as going to an outside job.
Interestingly, there used to be a sentence in the UK called “At Her Majesty’s Pleasure” where the prisoner did not know how long he was in for. It was deemed against human rights and banned, rightly so.
Our countries or regions thereof are/were turned into open prisons where everybody has been found guilty and sentenced to not only an unknown term, but a term that gets extended at will. Human rights lawyers would be all over this if it was a single prisoner.