BYU reported 1 case..... yeah, I am going out on a big limb speculating that the reporting was being suppressed, something that the advisory council report clearly states is an issue.
The report uses plural "assaults" and references a few different victims as having responded during the comment period, so saying that underreporting is my opinion is factually based in the context of the report.
You seem to be trying to protect BYU based on your personal experience, even to the point of being at odds with the official report? I am not sure what you are trying to prove here.