The 16-year-old's mother Angie was furious with the outcome.
Speaking outside Liverpool Crown Court on Monday, Angie Mayze said: "I'm disgusted. Drug dealers get longer."
Jason – known as Jay-Jay – received a fatal stab wound on January 13 this year.
Bosher Uddin, 37, had been due to face trial after being charged with murdering the teenager following a confrontation.
But his guilty plea to manslaughter, on the grounds that he had not intended to kill or seriously harm his victim, was accepted by the prosecution at the hearing.
Judge Gerald Clifton, who had indicated that Uddin would receive three years imprisonment, agreed to a defence request for a pre-sentence report to be prepared but pointed out that did not indicate the sentence will be any less.
The court heard that Uddin had confronted Jay-Jay while he was at the back of the Balti Spice takeaway in Clock Face, where Uddin was employed. John Bromley-Davenport QC, defending, claimed Uddin was using a knife in the kitchen when he was told that a theft was taking place from the container outside.
He dashed out with the knife in his hand.
There was a confrontation between himself and Jay-Jay, who was holding a box of chicken, said Mr Bromley-Davenport.
Uddin was still holding the knife and they started scuffling.
Mr Bromley-Davenport said: "There was a struggle between the two of them outside the container and he got him in a bearhug and the knife was trapped under the arm of Jason Mayze.
Bearhug
"He did not realise anything had happened. After he came away from the bearhug he saw blood and thought he himself had been injured.
"There was no deliberate intention to hurt him, it was an inadvertent act. He did not realise there had been a serious injury."
Jay-Jay, a former Sutton High Sports College student, had been stabbed in the armpit and was taken to hospital where he died three days later.
Stephen Riordan, QC, prosecuting, said that there were no prosecution eye witnesses.
He told Judge Clifton that the injury was extremely unusual and rarely found.
A pathologist was unable to say how it had been caused.
He said that a scientist, who examined the blood deposits and damaged clothing, found that Uddin's account in interview about how the injury was caused "may well be correct."
Outside court, Angie Mayze and other relatives expressed their anger over the situation and claimed that it had been a racist attack which the police had not investigated properly.
Mrs Mayze said: "A Union Jack floral tribute left at the scene was destroyed."
She also reacted furiously to the claim that her son was a thief and said he had never been in trouble.
She added: "He had a fiver in his hand for food. When the ambulance got there he still had the fiver in his hand."
Uddin, who had been on bail, was remanded in custody until August 25 when he will return to court for sentencing.