The fact of the matter is his legal status in the UK is still being investigated and his criminal offenses still to be prosecuted. Maybe he will get some hefty fines later, imprisonment or deportation.
His criminal offences have been prosecuted & he's been jailed for them.
What's happend here is he refused to tell them where he's from so they can't deport him, they then kept him banged him up for a further 5 months wilst trying to find out his country of origin because they knew he would do a runner.
I don't see this as any different to you or i refusing to give the police our name and address when we get pulled, IE you or i would get banged up untill such a time we either tell the truth or they find out our name and address by other means.
And sorry D.P if i went to spain and got jailed for over 20 offences and then refused to tell them what country i came from wilst they tried to deport me, yes i would expect to stay banged up.