I guess the article says he was being questioned. But by now, they have to know whether he was the driver or not and arrested him if he was.
They have lots of video of the driver. The cops know if the confessor was the driver or not.
The DA and Judges are available 24/7 to charge, if releasing ID is waiting on “charged”.
The only plausible reason for not releasing perp’s ID is the three reasons I posted.