Yeah, it is confusing, but if you're unsure and don't want to break the rule unknowingly, or waste typing a long post only to have it yanked, then maybe you can post an advisory post:
"I would like to review MPA x from MP y, but I am not sure if either fall under the NRP" ... anyone know for sure?"
If someone replies that they are covered by the NRP, or if the Admins yank that post, then you can be pretty sure that you shouldn't post your review.
If that post does get yanked, then there is still a chance that PMs can come into play to spread your information (I'd suggest that when releasing information via PM you only do so to those you can verify have a posting and contribution history that gives you a level of confidence in the requester being who they claim to be; an interested and legitimate hobbyist, and not some LE, creep, or total leach.