You're right, it does query the remote machine. The effect is the same though as long as it's on.
The case of the "a" doesn't appear to matter. I just checked... you can put -a followed by either an IP or hostname. -A, only an IP. This is on XP. In a domain, it will also show the logged on user, but not being in front of one right now I can't see the type code for that.