How is that different from withholding them?

Because right now his base is mad at his underlings - Bondi, especially. They can blame the deep state, the AG, the system or the process, or even the courts. His base still gets to believe in the conspiracy, and they get to believe that the conspiracy doesn't involve Trump, for a while. And they're still looking forward - they still believe the files are important, and that they might get to see them, so they're focusing on that.

But once all the files are out....there's nowhere to hide any more. That's it. It's done. We've seen everything. Either the base was heinously lied to by all their favorite influencers about a big part of their worldview, or Trump has to be in on it. The conspiracy metastasizes. Trump is no longer their savior, no longer the one who was going to fix this. Either he's helpless to fix it, or he's in on it. Neither is good.