This is not true. There have been multiple stories, such as the two journalists released a while back, that they are kept in small cement cells, often without light. It may vary depending on the person but I haven't heard someone being held in anything other than a typical prison cell.
They aren't beaten or physically abused but they do undergo some long-lasting psychological abuse.
Their stay usually lasts months as well.
Of course the NK story is very suspect. We need more information, but it seems unlikely that we'll get it.
There hasn't been any US prisoners in NK who were physically abused during their stay for PR purposes. I'm curious if he sustained a fall or some other accidental injury. Maybe he caused it himself and didn't get proper treatment.
He was held for an unusually long time compared to most people.
But the way he was taken care of and returned (they could have claimed he died) seems to suggest that he was not put into this condition on purpose.
If they claimed that a man in his twenties had died of a heart attack as they did with Japanese citizens they abducted, that would have been an even bigger scandal.
The news coverage of the incident has seemed rather strange to me. Nobody would be shocked if he had exited an US prison in a coma, although I guess people don't get out for "humanitarian reasons" in the US. (Except once every 4/8 years, I guess)
I mean in the US they regularly cook prisoners to death http://www.motherjones.com/crime-justice/2009/09/dog-days-tu...
Obviously NK overreacted for talking a "propaganda poster". He got XX years hard labor. But a westerner is normally kept in a hotel room in NK until an agreement has been reached and then he is released.
Warmbier had his medical "incident", as far as I know, over a year ago. So they must have fed him artificially and cared for him since. Also, AFAIK, they send an NMR image of his brain to the US doctors before he was released. I doubt that many North Koreans have access to this level of treatment.
So unfortunate this story is, I advise to use caution before reaching quick judgments.