Looks like saturation. Never really dries out and now moss/bio growth has attached to the edge as well.
The roof looks like it is at or near the end of its life in the photos.
No support under the shingle, excessive amount of shingle hung over the drip edge.
Welcome to the forum, Michael. Enjoy!!
I agree. …
That’s usually an indication of a homeowner installation. They think they are doing something good by leaving a little extra (probably in the same homeowner’s maintenance manual that recommends caulking everything on the roof). Eventually the shingles can crack/break away but the biggest problem is anyone cleaning the gutters gets bloodied fingers.
Shingle overhang should be about 1/2" past the drip edge. To me it looks like this install skipped the drip edge and they installed the shingles with extra overhang to compensate for this shortcut with hopes that the extra distance will keep water from soaking the roof sheathing.
High winds can grab the shingles more easily so now wind damage at the roof edge is more likely than if shingles were installed per manufacturer instructions (and building codes).
I think we may be talking about two different things. The bend over the lap or the actual cut edge?
The correct answer is:
Welcome to the forum, Michael.
Whether the shingle is installed at the eave, or the rake, starter shingles should overhang the drip edge no more than ¼" to ¾" inch. Remember, most shingle manufacturers recommend Drip edge flashing be installed. Typically/Normally, the finish shingles, the shingles atop the start are installed flush and aligned with the edge of starter shingles.
Now draw your thoughts to gutters below. If a gutter has a 4" reveal, the starter shingles impede the gutter pan trough width by the length of the overhang. 1/2" to 3/4" inch. The longer the overhang, the less the gutter reveal which may/can allowing water to spill over the gutter depending upon the slope of the roof. When you see long reveal/overhang, look on the ground for trenching to complete your hypotheses.
Hope that helps.