Hi,
sorry, I forgot to reply. We have discussed this to a great extent - and the result is: We do not want to change this. This is essentially what a Frontal mapping does, maps the HDRI (or other bitmap) entirely on your screen. What's behind the camera and what is reflected is basically a result of this - there is no more of the initial file to map there, since it is all in front of the camera. Repeating the map behind the camera makes no sense, because viewing the reflective surface from an angle would create a very clear line between the two planes.
We were thinking of removing the Frontal mapping option from reflection overrides so that it does not confuse users, but you should not use Frontal mapping on environments with reflections, generally.
Thanks,
Jan