I think they're guidelines for the construction of cycle paths, rather than for their use as such (though obviously one should inform the other). At least, that's the only context I've seen that said in. ICBW
Be that as it may, when I said "somewhere around the upper end of acceptable speed for a shared use path" I quite deliberately did not specify whether it was above or below said limit. :-) Depends on circumstance, though. A wide straight and empty shared-use path with good sightlines is very different from a narrow or twisty or well-trafficked one.