I have never seen this. See pic of house and you see the “roof” shingles are almost vertical. Could not find the manufacturer. At the end of each shingle they had stapled the bottom of the one under it. I think it is to keep the shingles down in 100 mph winds. But I have never seen this and it strikes me as wrong. But with the vertical plane of the shingles, is it a big deal?
For very steep pitches like that, it is usually recommended to dab under the tabs with approved roofing adhesive. I doubt any manufacturer recommends top-stapling the tabs. I would call that out as a defect in workmanship, which may end up requiring a new roof sooner than later.
Agree with Brad, Page 93
Failure of asphalt shingles is not uncommon on steep mansard roofs. There isn’t really enough weight to make them bond well so they suffer a lot of wind damage. Thus, Brad’s point.