I'm not disagreeing with your point in anyway, but just a point of reference: the article is talking about American jails, as opposed to American prisons. If I understand it correctly, once convicted, most people would be sent to a prison.

I don't think such a distinction is made elsewhere (at least not in the UK).

For reference, post-conviction, those sentenced to a year or less remain in jails, while those sentenced to a year and a day or more go to prisons. Prison is actually preferable over jail for most incarcerated individuals, as jails tend to be more tightly controlled than prisons, which function like their own societies with built-in, tractable hierarchies. People in prisons behave, in a sense, because they have to live together.

Well, that’s the point. The larger the population in jail, the more likely you will have deaths in jails. It doesn’t means the death is caused by the imprisonment. Particularly for a high risk population.