Who said we have to or should use the trans prefix whenever referring to someone who is female? If a trans woman is a woman, then they are a woman. I don't have to refer to them as a trans woman every time I refer to their gender identity.

Yet some people want to keep the trans identity because, even though they have used medical interventions to become physically female, they don't identify as CIS and want to honour their journey.

Others choose not. It's not up to me for decide for other people what identity fits best for them, and I will respect what they tell me.