Sounds like he's just fishing for work to me.

How worn are your pads ? Does the groove match the size of the pad, so is down to normal wear ?

There's no way that discs should be wearing out before pads if replaced together, in my experience.

To give you an idea of typical wear, I did around 75k miles just over 8 years in my old Focus and only recall changing the front discs twice during that time and the second was only a year or so before I sold it. My current Mazda 6 is on it's original front pads and discs at 55k miles and there is still plenty of wear left in both of them !

I'm pretty sure my discs wore down by a fair few mm each side before they started flagging up as needing replacing in the past.