Practically from defining data sovereignty as _control_ I agree, from a legal standpoint and how this is practically implemented that is a little murkier. It is often more about where it is stored at rest and who has jurisdiction over the data (c.f., Microsoft v. United States (2016)).
So in this case I'd argue it is less a question of "does the data leave the borders" and more "who has the right to the data" if that makes sense.