Counterintuitively, the criminology research by criminologists who study the data on such things shows there is a much lower recidivism rate associated with open prisons. The longer a crim is kept in a closed prison, the higher the rate of recidivism.
For example, the recidivism rate in Scandinavia where open prisons are the norm is only about 20 per cent. In the USA where prisons are draconian and worse, the recidivism rate is 70 per cent. So it makes economic and social sense to have fewer crims coming back for a second stay at HM's expense, so it makes sense to use more open prisons.
The old theory that harsher penalties lead to lower crime rates has been disproven over and over, supported by the data. The crime rate was quite high in Charles Dickens' times when death penalties for minor crime were common, along with transportation to the colonies etc, public floggings etc etc.
But of course, politicians today constantly cash in on public perceptions and fears and talk up harsher penalties so they can appear "tough on crime" and win votes. And the media beats it up for all its worth because manufactured outrage sells newspapers/generates clicks. So people wrongly assume that tougher jail terms would reduce crime because that is the (false) message they are bombarded with by self-serving pollies and media types..
It does seem pretty awful that old mate the child trafficker should be getting it so easy so soon after such a dreadful crime against children. However, for every occasional bad egg like him who legs it, there are thousands more who do their time and do not re-offend. So that is the end game, I guess.