Actually I think it's a hell of a lot simpler than that.
People do not, at a fundamental level, understand how search works. In particular, they do not understand how an email archive is different from a large pile of papers.
If you mention something in a printed memo (let's pretend such things still exist), and then the person who does that is immediately scolded for doing so, you've created 2 internal memos and probably stemmed the problem. Auditors MAY be able to find that, but it's a huge manual search to do so. The cost of finding those two items is substantially higher. Perhaps more to the point, you could probably destroy all copies of those physical memos. Bottom line, if there is a physical artifact of the communication, it is both harder to find and easier to destroy when there are fewer of them.
This is not how indexed search works. We all know that; if we work in tech we have probably deeply internalized it; if we grew up on the concept, we may have always understood it. A keyword is as easy to find in one document as in hundreds; indeed, it's EASIER to find in one document than hundreds, because there's less to sift through. The word "radar", by itself, is probably all you'd need to find these things very quickly.
It's also nearly impossible to destroy all records of the communication (and that is, itself, illegal under SarbOx).
So this is not evidence of someone wanting to get caught, it's evidence of a flawed internal model of how communication works in the modern age.