Why was Albus so insistent on this deception?


Albus initially portrays herself as male, though we later learn she is female.
She was strangely insistent too, going so far as to emphatically say,

> boku wa otoko da! (I'm a man!)

Her high level of offense at getting mistaken for a girl seems a bit odd. I'm
not entirely sure what she even gains from this. Was it to make sure the other
two main characters don't learn

> that she's the granddaughter of Sorena?

Is that the only reason? Because I would assume that there were many other
female witches in her order, so I doubt suspicion would immediately turn
towards that conclusion. However, as far as a guarantee, I suppose pretending
to be male could be argued to be an optimal way to divert suspicion. But is
this the whole explanation?

