To be fair it’s genuinely a super common mistake. I see redacted documents often at work (I do nothing fancy, just some privacy policy thing we deal with) and on like 30% of the documents we get you can either just highlight the underlying text or literally click and drag the black box off of the words lol.
I guess what happens is people can redact it such that they can no longer see it in their particular pdf software but then a different software can bypass it