I didn't say that no doctrinal difference exists, only that Anatta is highly compatible with the truth of a Higher Atman. You only mentioned Higher Atman in your previous comment, not common, individualistic meaning of Atman.

For that matter, even Shankara's description of the Atman is entirely in the negative, stating what the Atman is not. So even while accepting the existence of the Atman, he's clearly tending towards a universalist description that, again, is quite compatible with a practical understanding of the Buddhist doctrine of not-Atman.