Even if you knew it was "valid Unicode", that still doesn't gain you much. There is nothing you can do with a "valid Unicode" string without any extra context t

Even if you knew it was "valid Unicode", that still doesn't gain you much. There is nothing you can do with a "valid Unicode" string without any extra context that you can't do just as badly as with a byte string. And I'm putting "valid Unicode" in quotes because it's very much possible to have a string composed of well-defined Unicode code points that are nevertheless not a valid string in any meaningful sense, e.g. a string composed exclusively of LTR markers or accents.