It's unlikely that they meant "preferred pronoun" to be about a singular person generally, since it commonly refers to preferences about oneself.
People often use pronouns other than the ones someone prefers for a variety of reasons: sometimes the preferred pronoun is new, sometimes people forget, sometimes people don't respect that person's preferred pronoun.
People often use pronouns other than the ones someone prefers for a variety of reasons: sometimes the preferred pronoun is new, sometimes people forget, sometimes people don't respect that person's preferred pronoun.