Why should they have a lower burden of proof?
The exceptions are related to things like civil asset forfeiture, which are of questionable constitutionality and are similar to the rules we're discussing insofar as they are both worthy of contempt.
The protections afforded to both the accused and the accuser are to provide safeguards for everyone involved.
Because it's not a law, it can't be ruled on in court.
Because it can't be ruled on, they use this form of arbitration to solve what would be a civil matter if the school was a private entity.
Its not nearly as unreasonable as you make it seem.
The point in this case is that it isn't. Both the policy and the procedural rules are imposed by federal requirements.
If it was actually a policy of the school then it would be non-uniform and students could avoid schools with unreasonable policies, or push for changes to the local policy that are more achievable than it is for an individual to change federal policy.