I know that racking of composition shingles can leave a distinct vertical pattern curling on the roof surface. See the attached photos of the 2003 roof I inspected today. Notice the diagonal pattern of the curled tabs. None of these end tabs were properly bonded to the shingles below and there were multiple areas of wind damaged shingles including blow-offs and creased shingles.
This looks to me like the roofer installed them using a variation of the typical racking method, but on the diagonal instead of straight vertical.
Any other theories?
Notice the big patched areas on the roof in the background of the first photo