Pre-aos Spirit Speak was used to give the ability to understand dead characters and did not have any healing powers.
So if I had to guess from a RP point of view. You're speaking in a spirit language that has no gender.
Spirit Speak sound is (0x24B spirtspk.wav) for anyone interested.
But that is a neat catch, I'd never thought about it until now.
Better yet, why are there no female models or sounds for monsters? (speaking of the vast majority mostly, there are some female gender mobs in the game)
and further more, why was there never a Queen British! heh..
(Yeah i know when uo was made it was geared towards males around the age of young adults)