AgentLozen :
I wish there was a middle ground that would satisfy everyone. Maybe you could pick out some fans to stick in this case and then add a warning paragraph before the testing results that details what fan you used in the case and that the results are only supplied for the sake of showing this cases' potential. **Results may vary**
I've also wondered about this before. Most case manufacturers (including us) will typically use a 7-blade 1,000RPM 120mm fan when including a standard non-LED case fan, so something with those specs could be a good base reference if this kind of testing is ever done. And if it's from an OEM manufacturer like Yate Loon or Adda, then you don't get any of the extra little airflow benefits from more advanced designed by Noctua and others.
This would create extra work for the reviewers though, and the testing they already do can take hours or even a full day. First the full tests would have to be done in the stock configuration, and then all of the tests would have to be done again with all fan openings filled with the reference test fans. This wouldn't tell you what the cooling potential is with high-performance fans, but it could give the reader a better idea of what the case can do.
I actually asked OCC about that once when we sent them a case for review. The answer was the same as Steven's though, and I understand the reason, so I won't complain.