I'm generally supportive of our system of parole. I think, in many cases, it can be a way to continue rehabilitation while supervised on the outside. If we believe that prison is about rehabilitation as well as punishment, then it is a good concept when we'll supported and done well (that probation is badly funded and barely fit for purpose is just like everything else in the UK at the moment)
However, rehabilitation seems to be impossible for these kinds of offenders and there does need to be a distinction made between child abusers and other criminals.
These people are known and proven manipulators. They can say what they need to convince a panel they can control themselves while having no desire to do so whatsoever.
They should have to serve their whole sentence in prison and be on a permanent suspended sentence for life afterwards.