NWP, you're missing the main point - it has to be detention centers because the punishment for their crimes needs to begin immediately.
I did note that is was for punishment purposes... as this administration prefers, but the court has prohibited. In many cases there is no basis for punishment (but they'll do it anyway), and they WANT to have a case backlog, because then they can punish them longer. The current process is irredeemably wrong, and punitive, and inhumane, and that is what they want. How Trump broke the Immigration Courts (politico) If it was about processing, they'd hire more judges.