I guess the big question then is the relative age of Heidelburg remains in Europe and Africa. If the African remains are significantly younger, then they could have come from Europe or the Middle East, and don’t forget that the Mediterranean has been dry at times or much smaller.
It has to do with whether fossils from outside Africa are considered part of the family tree, rather than being an unrelated or extinct line -- that where the "out of Africa" bias comes in. See?