Guys, hold on your horses...if the groove is just in the surface, i.e. there is no deep groove and it can be felt only scratching the nail over it just wait... I had it and met with a Mazda engineer at the dealer by chance and he told me that it is the coating material and will go away alone and guess what? 2500 miles and all disks are smooth as a baby butt.... Mazda 1x0.
Now, the dust in the rear brakes... no explanation... Mazda 1x1.
So, unless it is really a groove just wait a little it can save you rotor surfacing.
Cheers.