I don't think they need to cover anything up. They can 'evaluate' the facts however they want. Their standards or interpretation of the facts might not be the same as a DA's standard for prosecution or a jury's standard for conviction, especially when they got millions upon millions of dollars at stake in terms of a television franchise and a lawsuit. Of course they're gonna say 'nope she wasn't too drunk to consent' when they're the ones who supplied the booze.

To be real, I feel like dude probably didn't do anything wrong. But WB's investigation wasn't about whether or not dude forced her to do anything. They're just saying, we don't think she was that drunk, so not rape. Too Drunk To Consent is one of those things with a lot of gray area.