This was a classic example of New Zealand's "ludicrous" parole system, Sensible Sentencing Trust chairman Garth McVicar said.
"He is making a mockery of the system which, as it stands, sanctions this sort of behaviour," Mr McVicar said.
"I think the victim would agree that Shannon should have served his full sentence."
Mr McVicar said Shannon's feet should not touch the ground when he was "dragged back to jail".
"This sort of thing can open old wounds and drive victims back to a place they don't want to be," Mr Mcvicar said.
He believes the parole system should be scrapped in favour of a judge-given sentence to be served in full.
"The system is absolutely crazy and it's no wonder it doesn't act as a deterrent," Mr McVicar said.
Inspired by the film and TV series, Jackass, the incident happened at Shannon's 17th-birthday party in 2011.
The victim, then 16, was held down by Shannon's friends while he was doused with petrol and set on fire.
The boy suffered third-degree burns to his body and still bears the psychological scars.
The three young men accused of holding down the teenager while he had petrol poured over him have had all charges brought against them dismissed.
The three, Jayden Wardle, 21, Michael Downey, 20, and Daniel Downey, 19, had been set down for trial on charges of causing grievous bodily harm. But charges were dropped in 2013.
Downey told Hawke's Bay Today he had moved on from the incident.
He had distanced himself from Shannon and the pair no longer spoke.
"Shannon has done his time so I'm not sure why he's done a runner," Downey said. "I think his sentence was definitely just."
Shannon was released in December after serving two of his three-year sentence. At his progress hearing in March, Shannon's rehabilitation appeared to be going well and he was grateful for his early release.
However, he had since breached his release conditions.
Conditions of his parole included attending counselling, residing at the same address and to attend a medium intensity rehab. Police want to hear from anyone who knows of Shannon's whereabouts.
They should contact police on 831 0815 or leave information anonymously on Crimestoppers 0800 555 111.