I checked an old email of mine and it says I have been an AAdvantage member for several years already. So that means I was in group 6 every single time then boarding right?

Also, I'm confused but how can someone not be an Addvantage member? If you are going to book an American flight through AA, then don't you need to be an Addvantage member? Or you don't? The only thing I could think of is you book your American tickets through a 3rd party like Orbitz and when you do that, say you buy basic economy, you are the last group to board which is group 9? If you book main cabin on Orbitz, you are group 8? But if you book basic economy on AA website, you are automatically group 6?