I've never thought that it had to be covert or even nefarious to be a MITM. It's a man-in-the-middle if it's sitting between two endpoints talking to each other and intercepting the data stream.

For instance, I proxy all of my web traffic in order to be able to filter my HTTPS streams. It's neither covert nor nefarious, but is still a man-in-the-middle. It's just not a man-in-the-middle attack.