What is a "good eater?"

My almost 5 yo daughter out of the blue the other night said, "Daddy, good job eating!" My jaw dropped. I can ASSURE you she has never heard anything like that in our home. I imagine this is something someone has said to her at school, perhaps a grandparent, though with all my gentle (mostly) reminders about letting her decide how much to eat, I doubt it was them.

I said, "Why do you think Daddy did a good job?" M replied, "Because his plate is empty."

I was getting up to refill our serving bowls and said, "That doesn't mean he's a good eater. Eating isn't good or bad, you have meals and snacks and eat when you are hungry and stop when you are full, even if your plate isn't empty..."

I hope I am not witnessing the well-studied phenomena that children under 5 will stop when they are full, regardless of the initial portion served, while children 5 and older will finish the entire portion served them, even if it is much more than they would have eaten if they had served themselves.

This notion of praising for eating, or relying on external cues for when to stop eating is not OK with me.

Also, I am curious, Gentle Readers. At what age does a "good eater" go from being a child who will clean their plate, to being a someone who will leave food behind or stop eating before they are satisfied? Crazy, crazy world we live in.