That part... nothing, I think it's a good idea as well.
In fact, there is a specific exemption in the ECHR to permit forced labour in the context of penal servitude.
It's more - inappropriate clothing for the environment, inappropriate living accommodation, unsanitary conditions.
Ultimately, these people are still humans too.
Why do we get upset at the sight of little African children running around in barely any clothing? Yet, in this context it's acceptable for prisoners to be doing the same?
I'm not saying that they should be given Nike trainers and so forth... but if they are living in outside accommodation (tents), then protection from the elements is required - otherwise in 20 years, there will be claims from ex-cons that the prison caused their skin cancer.