Abnormal Break Pad Wear on Ford Endeavour

While my Ford Endeavour was at the dealer for a 20,000 km third service, I got a call from the service adviser letting me know that my rear brake pads would need to be changed. I asked, “Why only rear? How are the front brake pads?”. The service adviser told me that the front were good for another 10,000 kms, but the rear would need to be changed. I found it a little weird because most of the braking load falls on the front wheels.

But assuming that he knew best, I instructed him to go ahead. I was out on a business trip and my driver took delivery of the car after the service. Today I had the chance to look at the old brake pads left in the SUV and found that the pads had quite a bit of life left in them. But one of them had disintegrated. So this explains by the service adviser wanted to change only the rear set and not the front.

But here is my question. The SUV is still under warranty. However, the dealer charged me for the new rear brake pads. I understand that brake pads fall under the regular wear and tear category of parts and are not covered under warranty. But this doesn’t look like regular wear and tear to me. I can break away parts of the pad with my fingers.

Do brake pads disintegrate like this under normal conditions? Or does this appear to be a manufacturing defect which should be covered under warranty?