This was a story told by a single escapee from a prison camp who has since recanted some of his story.
Shin Dong-hyuk, who apparently spent some time in Camp 14, made the claim in an interview:
Shin was ignorant of everyday life in North Korea. He knew nothing about Kim Jong Il. Instead, he told a story that his American debriefer found to be credible and utterly astounding.
Blaine Harden, Escape from Camp 14 (2013), p.161
The author of this book added an apologetic foreword following the revelation that much of Shin's timeline was false:
Shin now claims that "Escape from Camp 14" is a "sanitized" version of
his life, one he created out of a mixture of shame, confusion and the
impulse to avoid the most brutal of his memories. In an apology posted
to Facebook, he said, "Every one of us have stories, or things we'd
like to hide."
He maintains that he was born in Camp 14, but now says that he was
transferred to the lighter-security Camp 18 at age 6. He lived there
with his father after his mother and brother were executed. After a
previously undisclosed escape to China, he was recaptured and
transferred back to Camp 14. There he was tortured, to lengths he
never admitted before. This torture took place at age 21, not 13, as
he originally claimed.
In previous memoir scandals, these kinds of revisions have led
publishers to pull books from the shelves or heavily revise them. But
for "Escape from Camp 14," no details will be updated. Instead,
Penguin will add a new foreword to future printings and e-book copies.
Harden made the new foreword available online, and in it he explains
how Shin revised his story. He also acknowledges that he still has
doubts about Shin's account of his life in North Korea.
"Shin told me he is now determined to tell the truth," Harden wrote.
"Regrettably, he has told me this before. It seems prudent to expect
North Korea's most famous defector changes his story, MPR News, 2015
This is not to detract from the fact that we know of over a dozen North Korean prison escapees who attest to extensive use of torture and frequent deaths in their prisons.