I think you understand the message perfectly.
None of us can provide our birds with a 'Perfect Home', they are meant to be free without the stresses us humans provide.
I believe the stress meter is great & a good guide to represent what kind of impact our lives have on our birds. It is easier to convey this in a graphic form so more people 'get the idea'.
I have also had birds(2's)for many years & only 1 plucks (so far.) I believe I am very lucky in this regard & because I also know that my well adjusted, easy going, raised to the best of my ability 2's, could pluck or mutilate on any given day. I don't take their lovely feather condition for granted. It doesn't mean they are 100% happy or content to be caged.
I wish you the best with Eden & I believe she is fortunate to have you..