I never have heard anybody describe that as an exploit. It is an easy was to get your commanders killed. If your enemy uses this, just put a very large block of archers at the front line, set to shoot closest (With range 30 they can hit the enemies in the back). Even better if the shooters are strong like storm demons. I love enemies that make it easier for me to target commanders.
Usually we call things exploits here when you cannot do anything against it. Scout blocking movement, shooting commanders orders stealing, hidden pan fort blocking. But this an exploit, nope.