6 pots generally have a low pressure spring behind the largest piston to keep it in light contact with the disc, they are designed for race applications and this spring helps combat pad knock off (as racers hate it as it can be dangerous)

We do the same with our 6 pots, and so do AP on some of theirs. Its only a light 2lb spring so the rubbing is normal and far better than suffering pad knock off...

The grooves are for gas venting when bedding in new pads. Once they have been baked with the initial bedding in procedure the grooves are effectivly not needed as no more gasses are produced from the material.

A groove is not a WEAR indicator - that is measured by the thickness of the rotor. If they (the pads) have been bedded in correctly the groove is no longer needed.

If the groove is initially made deeper to be like more of a wear indicator you will suffer cracked discs in about 6 months time as the surface is made weaker.

Its done its job now if you have bedded in the pads correctly so stop worrying unless you want it for show