I'm not sure what you tested with, but it might "seem" that the original information is there? Only the original color data remains, but the detail is gone and

I'm not sure what you tested with, but it might "seem" that the original information is there? Only the original color data remains, but the detail is gone and each pixel position behind the redacted area is randomised/mixed. This randomisation step also overwrites pixel information so there is data loss as well. Because it's then blurred it looks like the info is blurred only. But if you'd be able to reverse the blur you'd end up with pixel noise. I find it hard to believe that that noise could be reverted.