Not really ironic or related. The privacy here is, well, keeping the tools entirely private -- no distribution or highly limited distribution, not obscuring their function.

Irony would be applying obfuscation or other DRM protection techniques to tools intended to de-obfuscate/reverse engineer which are then distributed/sold. This is fairly common in commercial reverse engineering solutions, although I don't think the irony of the cat and mouse game is lost on the authors in that case...

why not - after all, none of the open source licenses say that you must actually distribute the program, they only say that you should also include the source code if doing so.

Different motives. Think of it like encryption: when someone finds a weakness in a cypher people will generally move onto a new cypher that’s harder to crack. The difference here is the purpose of writing those tools isn’t to improve security, it’s to break code open. So keeping these tools hidden keeps them effective.