Why? Because it's the one I see the most that has this problem.
For the most part, I find Music Bee actually has little problem showing non-square covers and corrects it automatically. It's only when I see them in mp3tag that that I constantly have to right-click the picture and change the aspect ratio.
I have to constantly go back and forth when I add album art to new folders tagging since the previous setting carries over when I don't want it to.
I thought somehow this kind of a setting display would embed itself in the individual tagging, but I guess that sounds impossible now.