I think this example shows more that the difference between vagueness and simplicity is dependent on the context. If I talk to somebody who has not read LW/rationality/IQ studies they have no concrete mental model of what it means to have IQ 130 (other than that the higher IQs are better). So then saying “you need IQ 130” and explaining in a convoluted way what exactly did you mean by that conveys less information than just saying “you need to be smart” and makes a simple statement more complex.
On the other hand, if I talk to somebody about whom I have reasonable expectation that they understand what the IQ actually means, saying smart is also simpler, but due to the abundant and less well-defined use outside precise conversations, it might make sense to default to more precise and quantitative statements to avoid confusion.
I think this example shows more that the difference between vagueness and simplicity is dependent on the context. If I talk to somebody who has not read LW/rationality/IQ studies they have no concrete mental model of what it means to have IQ 130 (other than that the higher IQs are better). So then saying “you need IQ 130” and explaining in a convoluted way what exactly did you mean by that conveys less information than just saying “you need to be smart” and makes a simple statement more complex.
On the other hand, if I talk to somebody about whom I have reasonable expectation that they understand what the IQ actually means, saying smart is also simpler, but due to the abundant and less well-defined use outside precise conversations, it might make sense to default to more precise and quantitative statements to avoid confusion.