Can the epicene personal pronoun be used regardless of semantic gender of the word?

In other words, for any word with semantic gender (i.e. lion, lioness, boy, girl, man, woman, cow, bull, regardless of self-identity, can the epicene personal pronoun be used to refer to these nouns?

Or should the epicene personal pronoun only be used in exactly two instances - when the gender of a person is unknown/irrelevant OR when a person chooses to identify with that pronoun?