So they can feminize your voice but can they also make your voice sound younger if you ask them?
I guess a higher pitch is associated with youth more than with age. But it is hard to define what makes a voice sound older. My guess would be that it has more to do with how a voice is used and how healthy it is than with things that could be changed surgically. A surgery can fix pitch and remove some of the "male edge" to the voice, if you have nodules or assymetry this can be fixed as well, those might make a voice sound more unhealthy and thus maybe more old?