Yes, the transparency and openness to suggestions is very appreciated.
Mmm I think I see what you mean, if I move the parent bone it will change the keyed world values for the child bone, and Bezier curves don't work there for that same reason (world values could change mid-animation if parent bone is moved).
Since this seems to be complex enough and may or not be implemented in the future, I wonder if it would be a good idea to add a small note in the documentation mentioning that the graph always works with parent values, just to avoid users getting confused about why the graph is showing different values than the toolbox.