Just because they are human sized doesn't make them Vasto Lorde Arrancar.

A Vasto Lorde is human size. But this is the arrancar we are talking about. So let's say a Gillian got turned into a Arrancar. (which I am pretty sure off. After they ARE footsoldiers) Then they would gain human size because Shinigami are human. So they don't have to be Adjucha's and Vasto Lordes. Not all of them anyway. I think he only has like 3 to 4 as Arrancar stashed somewhere in where ever the hell he is.