This is not normal tire wear, there is something wrong with the geometry of the suspension, as well as with the pressure in the tires
Especially in the first picture

 

"Very close to needing new tires" LOL

Excessive toe-in can easily do that. Also camber, but I think that is less likely.

 

You aren't "close" to needing new tires... those are beyond their service life. Replace them NOW.

Get your alignment checked. Something is VERY wrong with it.

 

If it were me, I'd get on my hands and knees behind one of the rear tires and sight along the sidewalls to see where that sightline hits the front tires. It should be close to the sidewall of the front tire.

If the tire is toed-in too much, the sightline will be aimed at the car door. You need to do both sides.

This is not as wacky as it sounds. I actually saw AJ Foyt get out of his car and do it in the middle of the 500 after "whitewalling" his right side. You can easily see a gross misalignment.

By the way, I sometimes align my own cars by using a laser-equipped straightedge laid against the sidewall in a similar manner. It's pretty accurate.

You can get rough idea of a camber problem by looking straight down on the tire from above. However, I think you have a toe issue because you say both rear tires look the same, which would be typical of a toe problem.

 

By the way, I sometimes align my own cars by using a laser-equipped straightedge laid against the sidewall in a similar manner. It's pretty accurate.

Thanks for the advice, I've heard this before, and after talking a look at the rear tires with a good straight edge they are both toed in, one more than the other. Sight line closer to the rear doors.
Inside of the rear tires actually has reasonable tread left, but know the outside are done.

 

On a recent trip to the airport, I passed two cars that each had a rear wheel that was more horizontal than vertical in terms of alignment. I wondered to myself how someone drives a car like that and doesn't notice...

You (and others) are lucky this didn't lead to an awful accident! I was expecting to see images of a bald line down the middle of your tire tread (caused by over inflation) or symmetric wear spots on the outsides of the tire tread (from under inflation). Definitely significantly out of alignment. Get new tires, then an alignment.

 

Appreciate all the responses, and glad to see so many non XC60 owner posts here. Like me browsing and searching the other model forums sometimes provides your answer.
Having some Continental ExtremeContact™ DWS06 Plus rubber getting mounted this weekend and alignment.

Really do like the stance from behind with the 275's but will stick with the 255's I have.

 

Ended up finding a set of XC90 All Season Volvo OEM Takeoffs. 275/45R20's with brand new Pirellis's, for about what new tires would have cost, also had the alignment done and one back wheel was pretty misaligned.
Haven't seen any real rubbing yet but they are a bit tight against the inner fenders when cranked to the stops.
Rims aren't my preferred color 10 Spoke Silver, but thinking I can powder coat if it bothers me that much.

Thinking about Fender Extensions - Pine Grey - Volvo (40003531).
They show this part as fitting 2019-2021 XC60. Any reason it doesn't fit 2018?