I understand that, he threw that joke in there. Thought I would share plus put a little knowledge out there for some who may not have known that.
Yes OP that is true and I was really surprised when I first heard about that as no one has ever mentioned it until job orientation. Basically "jobs" you get paid for when not driving is on duty.
Really, you wouldn't just log that as off duty, you wan to indicate that you spent that entire time in the sleeper berth.