Correct me if I am wrong, but we weren't introduced to the phenomena of getting a devil's power through their heart before Lucius? It also makes sense to me that he ate Astaroth's heart firstly and learned that way.
So, judging by what we've seen, the four wings and horns isn't something that most Supreme Devils have. Only Lilith and Namaah in their fused state, and Lucifero have them. So this could point out that Lucifero is more than one entity. Damnatio pointed out that he was also called Satan. Maybe Lucifero and Satan are the two entities (fused as one) that conform the ruler of Gravity.