I thought the plan was they would stay in Mexico until their cases asylum hearings!????
They were already in the US, illegally!
Current law restricts how long they can be kept in custody, and IIRC, they are given a “show up in court” date and released on their own recognizance.
IIRC, less than 10% of them do show up for their “amnesty” hearing. They just ignore the courts!