If this is the case shouldn’t we justifiably extrapolate that humans-endowed by the added attributes that other living creatures do not have of free choice-may also have the potential to change their sex to suit environmental factors or their own preferences? Especially since I know someone who had both female and male biological bodily parts and was asked what was it’s preference.
Mmmm...., I don't think we can justifiably extrapolate from amphibians to human beings. Those frogs change sex according to external stimuli which are governed by species survival.
Also, from our standpoint, sex has been karmically assigned and our biology does not allow natural changes, so it can be argued that wanting to change sex artificially means refusing to accept karma and we know well that this is a recipe for an unhappy life and future reincarnations where the same issue arises again.
The special case of a human with both male and female attributes is so rare that I wonder what's the karmic reason and requirement, that is, what is the androgynous person expected to do. By whom the person you know was asked about the preferences? Was the preference about the official sex and name?
