That is... interesting.
I have two scouts constantly running around using that command. I just tried it. With both scouts doing this, one reported CPU costs as you expect, but the other is reporting what you say, 7-11, sometimes as high as 20.
Oh man, I've spent the last week optimizing my worker code because of my CPU Spikes. But I just watched my CPU spikes happening exactly with my scouts using this command and getting CPU of 20+. Thank you so much, you've discovered my CPU hog.