Your first sentence isn't supported by your second and third. It is incredibly common to track not just interest but level of interest -- and lots of companies

Your first sentence isn't supported by your second and third. It is incredibly common to track not just interest but level of interest -- and lots of companies find it a valuable metric for marshalling their resources. Is this perhaps not the best way to get that metric? Now that can be a helpful question to ask and a good thing for this dev to think about, rather than outright dismissing the attempt.