Unfortunately, it isn't that simple. In theory, that is true, but it depends upon a number of other factors. One would be the overall reflectivity of the internal reflector, as well as the opacity (these reflectors are not completely opaque, so there is light loss through the other side). The other would be the incident angle of the light from the reflector. If the geometry of the reflector isn't optimized, it won't be as effective.
Now, whether or not UVL has accounted for all this enough to phase out external reflectors, that can only be accounted for with empirical data. Unfortunately, I don't have a PAR meter to verify any of it. Judging from their VHO reflectors, I don't believe they will be able to phase out the external ones just yet.
