He has a right to parole as his minimum term has expired.
The only thing the parole board can consider is whether he is safe to be released. It is not in their gift to make moral judgements about whether someone should stay in prison or to extend anyone's sentence.
If Pitchfork was convicted of the same offences now, he would receive a longer tariff - the sentencing guidelines have been changed since he was convicted. If sentenced today, he would in all probability receive a whole life order.
However, you cannot try someone for the same crime twice, and you cannot extend someone's sentence for the same crime beyond that passed down to them, unless the circumstances of said crime are found to have changed. This is for good reason - imagine for example if the govt had political prisoners and just kept increasing the tariffs on the sentencing guidelines for their crimes so that they were never released.
This point of non-retroactivity is key in law - you can't go back and charge someone again or increase (or decrease) their sentence because the laws have changed since their conviction.
Those outraged at the exercise of these rights would do well to remember that they are rights we all have in law, and we would expect to be able to rely on them if we ever needed them. We can't take them away from someone because their case is high profile.
So yes, it is correct that he is being released. Do I agree with it? Emotionally, probably not. Do I think the parole board have got it wrong? I can't comment - I don't have the evidence they have access to.