[NSFW] Why is futa "not to be tagged female"?

The detailed description for the ‘futa’ tag states that posts with futa should not also have the ‘female’ tag. Isn’t that what futa is, though?

For the purposes of filters and watchlists.

The actual Japanese word means hermaphrodite. We use the tag for feminine bodies with male genitalia. Neither of these things are what we use the tag “female” for.