There is no gain, there is not supposed to be. Virtu MVP is about response times, not framerates. The fact that framerates above 60 are inflated is purely incidental. The frames are not actually rendered, and in fact that's the whole point of the software.
If you're looking at Virtu MVP as something to boost your framerates, you're looking at it totally the wrong way. The fact that Lucid mentions boosted framerates on their product page is probably a large part of the confusion. They're just trying to make the product sound as appealing as possible, and are being pretty dishonest about what it does.
What the software really does is intercept the attempts to render frames. If the software detects that the rendered frame will be discarded, or will not finish rendering before the next time the buffer is sent to the monitor, it returns without doing anything. This frees up the computer to handle input, resulting in less input lag. It also makes the computer think it rendered the frame, resulting in an artificially inflated frame rate.
The "extra" frames never get rendered.