...they are the same person, but the voices sound like their fundamentally different.

The misopaedic voice sounds like it's being drawn mostly through the nose and has a hint a nasalness to it.
"Fayla"'s voice sounds like it's coming from the bowels, or rather the stomach and straight out the mouth, lacking any sort of nasal passage.

However, this could be imitated (I just tried it) by shifting and controlling the release of air when speaking.

I'm not sure though.

I guess the voices could have a common origin, but to me there seems to be something fundamentally different about them.
I'm interested in seeing how this ends up, but I have a feeling that it ain't going to be pretty.

I hope that that hunch is wrong though.