I wanna know who the rocket scientist was at the FMCSA who decided that this break had to be taken off-duty. IMHO it should be loggable as on-duty-not-driving. I mean, really: Would it be that much more tiring to be on-duty while you're sitting in the truck eating your lunch & playing Angry Birds on your phone, than it would to be off?
Why would you want it to be on duty? I don't see any upside to that. At least it's not going against your 70.