Oof, and it's too late for me to go back and fix it (unless Dang would be so kind, for posterity).
Definitely meant the positive version and I have no idea how I transposed those two! Apologies for contributing to the mess and appreciate you catching it. :)
Oh, well your meaning is obvious from context, didn't mean to nitpick you but was just curious about the trend I seem to be observing, so apologies back :)
I parsed "cannot be understated" as "must not be understated", or "we cannot allow it to stay understated". I took it to mean a call to action, "this cannot be x!".
Seeing this a lot recently[1]. I guess you mean the opposite of what this implies ("his impact is less than you could state"), but I'm curious how this has ended up being almost as commonly used as the "correct" form[2]. Is it an in-joke or reference I'm not getting?
1: https://www.google.com/search?q=%22cannot+be+understated%22+...
2: https://www.google.com/search?q=%22cannot+be+overstated%22+s...