While useful it needs a big red warning to potential leakers. If they were personally served documents (such as via email, while logged in, etc) there really isn't much that can be done to ascertain the safety of leaking it. It's not even safe if there are two or more leakers and they "compare notes" to try and "clean" something for release. https://en.wikipedia.org/wiki/Traitor_tracing#Watermarking https://arxiv.org…
This doesn't seem to be designed for leakers, i.e. people sending PDF's -- it's specifically for people receiving untrusted files, i.e. journalists. And specifically about them not being hacked by malicious code . I'm not seeing anything that suggests it's about trying to remove traces of a file's origin. I don't see why it would need a warning for something it's not designed for at all.
Like IDEs do when you open random projects