It says that when I have my MacBook right next to me in a laptop bag while I'm driving. I think it just sends out information on the last known device location so that if you leave that location, it lets you know. It can be annoying, sure, but it's saved me a few times when I left my laptop behind somewhere. So I'll deal with the minor annoyances over peace of mind that I didn't leave my tech behind.
So I don't think the laptop itself has some power-reserve mode for sending out location information, because like I said, it's given me this notification while it's literally right next to me, it just saves the last location data the last time it was powered on.
The newer iPhones, however, can still send out GPS location data even when the phone is turned "off" ... so these devices do have a power-reserve for GPS coordinates in case your phone is stolen or lost. They will probably implement these in newer laptops (if they haven't already, I haven't been keeping track).