Without looking at the discs, I couldn't say for certain, but I doubt the discs need changing. Unless there's absolutely masses of changes in the thickness of the discs and they are above the minimum thickness, can't see any issues with just changing the pads.
On the flipside, with the motor manufacturers quest for longer service intervals, the ratio of pad changes to disc changes has definitely shifted in more recent years. It used to be that pads were soft and discs were hard and the discs rarely needed changing, whereas nowadays it's more likely the discs would need changing too.
Either way, there's no way a decent garage could say that you need your discs changing without even looking at them. That's simply trying to wring as much cash out of you as they can.