How to register traffic signs
I would assume most taggers don’t know exactly what a traffic sign is called or what it means. Yes, even the ones with a driver’s license.
In that scenario, for most taggers to be able to register a sign correctly, it would have to be selected from a set of images based on what the sign looks like. The tag value can then be whatever is technically best suited.
Code vs. name
I read the main purpose of the proposal for traffic sign names as standardising traffic signs nomenclature across borders, not as a way of making the values human-readable. The codes (or standardised names) can easily be made (more) human-readable by the editor if there’s a need for that.