At the time Justice Paul Heath said that in the light of Nelson's culpability and having regard to his age, brain development and personal circumstances it would be "manifestly unjust" to sentence him to life behind bars.
Instead, he sentenced Nelson to a finite term of 18 years imprisonment, with no minimum non-parole period.
Nelson is now 19 and became eligible for parole this month.
Unless the board release him, he will remain in prison until April 15, 2030.
While eligible for parole, the board said Nelson "did not seek it".
"He accepts that he has more work to do before that is a realistic possibility," said Justice Marion Frater in her decision, released publicly this week.
She said the young killer needed - and wanted - more help.
"He is aware of the ongoing effect of his offending on the victims and their families," she explained.
"He said he did not think of the consequences of his actions. He cannot explain why he did what he did. He wants help with that process.
"The best explanation he could give was that, at the time, he was not disciplined.
Justice Frater said Nelson had been assessed with a medium to high risk of violent reoffending but had much more work to do inside before a release could be considered.
"He has yet to engage in therapy specifically addressing the circumstances surrounding the murder of his caregiver and related trauma," she revealed.
"The psychologist who wrote the report for the Board said that although Mr Nelson has done exceedingly well in custody, there is no certainty about his ability to manage future interpersonal conflict outside the highly structured and familiar custodial environment.
"He needs to be tested - however, before that can happen, he needs intensive rehabilitation.
"Because of his age, Mr Nelson cannot undertake any group programmes - and that would not be advisable anyway."
Justice Frater said Nelson was currently serving his time in a Maori-focus unit Hawke's Bay regional prison, following a three-year stint in a youth justice facility in Rotorua.
He had used his time in custody to acquire over 130 NCEA unit standards, achieving NCEA levels 1 and 2.
He hoped to one day attend a tertiary institution.
"He works in the external grounds party and is said to have a strong work ethic," said Justice Frater.
"He is deeply involved in Tikanga Maori and speaks te Reo fluently - he is an accomplished carver and mentors offenders in the youth unit in Tikanga and kapa haka."
Justice Frater said the board supported Nelson's participation in regular psychological counselling and, in due course, other appropriate programmes and "interventions".