Just so many things you can imagine......
...There're more mysterious things lied in the whip weapon. When the whip was equipped by the glitched Alucard with Soma mode/forced to be equipped by Alucard in the actual Julius mode, there's a rather strange diagonally swing which can be activated like that of Alucard Sword's diagonally attack (It's currently unknown why the situation happens; In most cases, it was possibly an unused variant of whip attack (diagonally attack) due to it was separated to the ordinary whip swing; Or perhaps it was the finish pose of whip swing which was meant to be part of Julius's normal attack, but they later changed to let the whip immediately pulled back to Julius' pocket)
Dunno why such a variant exists in the first place
If the tech that change Soma to Alucard hasn't been developed, we'll never know such a fact
(Costume Cheat in Action Replay thingy =/= Character change tech)