Sounds so logical to me. That's precisely because they are trying to figure it out that you repeat/praise. Exactly the same as when you "work on duration" as Bearshandler said.I have used the Good-command but I haven't noticed that my dogs had really paid much attention to it once they had learned the command. It was only during the phase where they were trying to figure out what I wanted that I noticed them really paying attention to the Good-command talk.
Just telling your dog he's doing something right, and that thing is (sit, stay, or about anything).
Of course the command gets associated with praise and the good feeling that comes with it. It is motivational.
That's probably why my dogs have two styles of heeling. One is like working-mode heeling, where they're trotting all proud, tail up, and watching me (the thing that looks pretty if you want to do a little show lol), and a more "off" heeling where they'll be walking in a relaxed, slow mode with ears flattened, tail lower, and a soft gaze forward.
That is because one mode is associated with a lot of praise and motivation, whereas the other style is associated with "moderation".
And still, for some reason, they totally get what "heel" means and adapt according to context and the tone in my voice.
They do not seem the least confused about what I expect.