the grooves are designed to prevent the build up of hot gasses during braking, and also de-glaze the pads.....
but in a landy you are NEVER gonna work the brakes hard enuff to make these features work, and even if you did you wouldnt notice the discs are the 'wrong way round'. i had oversize Brembo discs on 1 of my old heavily tuned cars (400bhp) and from experience i can tell you that the brakes work and feel the same no matter which way you put the discs on, you will bottle it LONG before the grooves in your brake discs become important