Not true. The measure of success in Starting Strength is 100% based on linearly increasing strength, with zero consideration to appearance aka "muscle growth."
As other posters have mentioned, it's well known that high-rep lifting will increase muscle mass, and that's what bodybuilders do. However, powerlifters don't care about anything but strength, so they use low reps, just as Starting Strength recommends.
So if strength is your main concern, like it is for Rippetoe and Kilgore, you would follow their recommendation. A higher number of reps with lower weight is certainly not just as good for strength development.
As other posters have mentioned, it's well known that high-rep lifting will increase muscle mass, and that's what bodybuilders do. However, powerlifters don't care about anything but strength, so they use low reps, just as Starting Strength recommends.
So if strength is your main concern, like it is for Rippetoe and Kilgore, you would follow their recommendation. A higher number of reps with lower weight is certainly not just as good for strength development.