Well, I've only been a DL for a few months now, so I may not have this completely correct. There are 2 issues with earning rank that you have brought up, participation and achievements. Achievements seem pretty black and white either the parents (or DL for Weblos) sign off or they don't. And it is a matter of do your best.
The bigger issue of interpretation I think is the participation issue. When I went through training, I don't remember this issue being addressed, but in practice in our pack, it is not taken nearly as importantly as the achievements. Some of the boys in our den sim