Correct, It has nothing to do with VTEC operation, it's just designed to help provide more torque at low-mid rpms... try switching it off on the fly, the motor breathes much easier and sounds more "buzzy" if that's the right term when the butterflies are open and the engine is using the short-intake runners for max power at HIGH-rpm. Also, with the butterflies closed, the engine sounds more violent and has an angrier less "buzzy" sound. Unfortunately I don't have P72, I have P28 with GSR program and a GSR head with matching IM, so I had to wire up a switch for the butterflies...
I use the butterflies closed for better start-stop street driving and A/C use and switch to open butterflies for Highway or racing.
Mike