The difference between instrumental and terminal values are in the perception of the evaluator. If they believe that something is useful to achieve other values, then it is an instrumental value. If they are wrong about its usefulness, that makes it an error in evaluation, not a terminal value. The difference between instrumental and terminal values is in the map, not in the territory. For someone who believes in astrology, getting their horoscope done is an instrumental value.
The difference between instrumental and terminal values are in the perception of the evaluator. If they believe that something is useful to achieve other values, then it is an instrumental value. If they are wrong about its usefulness, that makes it an error in evaluation, not a terminal value. The difference between instrumental and terminal values is in the map, not in the territory. For someone who believes in astrology, getting their horoscope done is an instrumental value.
In practice this criterion is frequently circular. See also the blue minimizing robot.