I should probably explain a bit more, they vibration is definitely only cause by the grooves, and not because the disk was warped/runout whatever.. The disks are only a few months old, while i was driving a few weeks ago the pad material tore off the backing plate after which the backing plate came in contact with the disk and created the grooves. As soon as it happened i stopped the car and got it towed home.
Before that incident, the disks were absolutely perfect, no vibration whatsoever, and as i said, nearly brand new.
When i dropped the disks off one was 29.95mm and the other which had the grooves was 29.74 as measured in the grooved area. When i picked them up the good one was 29.18 and the grooved one was 28.99.
So not only did they machine slightly more off the one that was perfect, they are different thicknesses. It seems they just picked approx 0.75mm out of their arse and decided to chop that much off both without any thought.
I specifically told them when i dropped them what happened, and made sure they understood that they should only take the absolute minimum off. When i picked them up i expressed my concerns on why so much had been taken off and they just like well thats how much was required which seems to me complete BS.
I notice the degradation in braking performance as the disk thins out and i go through brakes reasonably quick anyway so it is a concern for me