Shawn,
As you quite rightly eluded to in your original post, it is VMC that is defineable. VFR are simply a set of rules that we may be able to choose to follow when flying in the defined VMC, but we have to apply the rules.
As Sasless pointed out, we could find ourselves flying in conditions defined as VMC but that does not necessarily mean that we can fly under VFR.
For Air Carrier Operations under FAR Part 135, - 135.207 says this:
VFR: Helicopter surface reference requirements.
No person may operate a helicopter under VFR unless that person has visual surface reference or, at night, visual surface light reference, sufficient to safely control the helicopter.
I'm certain you are aware of all the above but I hope the reference helps.