The Wikipedia's article about the fraction slash says: “The fraction slash is used in the display of ratios and fractions, as in constructing a fraction using superscript and subscript” (http://en.wikipedia.org/wiki/Slash_(punctuation)#Arithmetic
I don't read this to mean necessarily "a fraction using Unicode superscript and subscript characters".
Indeed, using superscript and subscript characters is not what Unicode intends, as can be seen in TUS section 6.2:
Fraction Slash. U+2044 fraction slash is used between digits to form numeric fractions,
such as 2/3 and 3/9. The standard form of a fraction built using the fraction slash is defined
as follows: any sequence of one or more decimal digits (General Category = Nd), followed
by the fraction slash, followed by any sequence of one or more decimal digits. Such a fraction
should be displayed as a unit, such as ¾ or !. The precise choice of display can depend
on additional formatting information.
The superscript and subscript characters are not Nd. Another piece of evidence is that the vulgar fractions have a decomposition that uses the regular digits.
I think that the Wikipedia text should be interpreted as:
The fraction slash is used in the display of ratios and fractions, as in constructing a vulgar fraction.
And the example that immediately follows is indeed using regular digit characters.