[codingismycraft]

I agree that the classification of a new feature or anything that has to do with the presentation layer is not exclusively a developer's choice.

More than this though, assuming that the stakeholder has a clear decision about issues related to UX (as your spelling error you are referring as an example)it is up to the senior developer to decide about the deployment readiness of the platform. As an analogy you can think of the distinct responsibilities of an architect vs a civil engineer in the construction of a building.