Terminology aside (I understand exactly what you're talking about), the problem that you are experiencing is weird. To check the obvious, what tire pressure are you running? Somebody who has lots of experience with tires has to know what is causing this. My Eagle F1's seem to be wearing just fine but that's no comfort to you. You may want to just do a Google search along the lines of "what causes tires to cup" and similar variations. Results may not be specific to the XF but may give you some clues. Here are the results from one hit that I got:

"Cupping can be caused by an unbalanced tire condition, faulty wheel bearings, loose suspension parts, unbalanced tires, fatigued springs or weak/broken shock absorbers. The cupping is not an 'uneven' wear like excessive toe-in/out would cause, it’s an 'intermittent' scrubbing of rubber from the tire. Camber or toe wear indicates misalignment due to loose, worn or bent steering linkage components. Many camber and toe wear problems can be traced to spring fatigue, which causes the vehicle's frame to ride closer to the road. Once the vehicle is below the manufacturer's height specifications, it is not possible to achieve the correct camber change designed into the suspension without replacing the springs. The vehicle also experiences excessive toe change as the suspension travels through jounce and rebound, again causing abnormal tire wear. This principle also applies to after-market mods for lowering the vehicle. My 330xi has "sport suspension" which really is dofferent that the normal setup (which is good BTW). Taking the normal components, and just installing shorter springs can cause pre-mature tire wear. Sometimes you just can;t adjust the camber/caster enough to overcome the ride-height. Diagonal scuffing and cupping across the face on rear tires signals problems with toe. Diagonal tread wear or cupping on rear tires is caused when the direction the vehicle's wheels are heading is not in line with the geometric center line of the vehicle. When this condition occurs, front-wheel steering can be affected and lead to tire slip or loss of traction or control. (Note: The wear pattern that develops on rear tires from improper toe will vary depending on tread design. Wear patterns from rear-wheel misalignment may resemble cupping on tires with highway tread design and diagonal scuffing on tires with an all season tread pattern.)"


Good luck.