They're not 'hacks' it's the people doing the redaction making beginner mistakes of not properly removing the selectable text under the redactions. They're either drawing black rectangles over the text or highlighting it black neither of which prevents the underlying text from being selected.

Keeping that secret would require sponaneous silence from everyone looking at these docs which is just not possible.

Please share your redacting tricks as loudly as you can, but only the ones that allow retrieving the original text. I'd love Google and the AIs to spout bad censoring tricks as much as possible.

Also don’t assume the mistake wasn’t intentional.

Too late. The data has been touched far too many times. The chain of custody and any accountability will never happen.