Indeed, which is unfortunately not as common knowledge as it should be.
I've pulled over for several riders on the side of the road with their helmet by their rear tire, thinking something was wrong, and meanwhile they were just stopping to make a phone call or taking a break.
Meanwhile, I've also stopped for riders who looked like they were doing the above (helmet on their mirror or elsewhere, but not on the ground) and they actually did need help.
It's actually not covered (from what I recall) in the MSF courses, though it really should be. There should be a standardized signal for "I need help!" and this technically is supposed to be it -- just not many people actually know about it.