It's unclear whether "breaking the law" includes speeding.
It's also unclear whether (former) prisoners must avoid breaking the law until their proper release date, or whether they must avoid breaking the law until the state discovers its mistake.
If it's the latter, it would be in the interest of an incorrectly released prisoner to inform the state of its mistake the morning after their proper release date. Of course, in this particular situation, the prisoners likely had no idea they were incorrectly released.
Just an assumption, IANAL.
Add to that, that the problem existed for 13 years. I would say that it's a non-issue, barely worth fixing. The persons that have been release earlier are prisoners that have shown good behavior, so I doubt that it will any more dangerous, despite the circumstances for their crime.
The law seems a little buggy to me though. Why does it even make sense that you can earn "good time", but only towards a portion of your sentence and not the whole thing? If you don't want people to get out to early just specify a minimum time that must be served.