I’m sorry to hear about your rear brake frustration but at the same time I’m interested in what you’ve experienced. We too purchased a dealer owned 2018 S60 in Jan 2019. The dealer had operated the car for about 9 months as a demonstrator and shop loaner. It not had 4000 miles on it when we purchased it.

Soon afterwards I noticed both rear rotors (Outboard surfaces) were already getting badly grooved. The outboard pads, however, were still nice and thick. I figured “Oh great, Volvo has bowed to the consumers that can’t stand a little brake dust on their rims and has built the car with some sort of rock hard ceramic pads.” I pointed out the deteriorating rotors to the dealer service rep who told me “Don’t worry, you’re still under warranty so we’ll keep an eye on it.” I have no idea what the inboard surfaces look like.

I also notice another oddity with the brakes - when coming to a stop on a slight uphill slope the car stops fine and then you know how a car will slightly rock backward after stopping? Perfectly normal for any car. But on this one, when the car stops and rocks back, I can feel the brake pedal sink ever so slightly downward. It’s quite subtle. For some time now I have pictured something wrong with the calipers like maybe the pistons are cocking a bit within their bores, allowing a tiny bit more fluid to flow into the caliper. I know that sounds crazy but after reading your testimony I’m thinking it might not be so crazy.

After 45 years of owning Volvos this Is the first one with the rear calipers doing double duty as an integrated parking brake. I’m not impressed. I plan to take the car to a different dealer and see what their story is. If nothing else, I can make sure the service rep documents my complaint in the service write-up in case I need to take elevate the problem to a higher authority.