Yes this is quite common. I would try telling them what you said here - "I know from my past experiences that my enthusiasm for the job is directly correlated

Yes this is quite common. I would try telling them what you said here - "I know from my past experiences that my enthusiasm for the job is directly correlated with the degree to which I perceive their projects will be both meaningful & successful." Then you can find a middle ground - maybe they can tell you about a past project, or maybe you sign an NDA, or maybe they can just tell you.