I would guess that if that is an upside down shingle placed there, that a leak was already detected. It appears that no kick out flashing was employed. And did the siding come into contact with the shingles or were you looking at flashing along that wall.
I'm not aware of code addressing this specific issue. R801.3 addresses general roof drainage, which this house may not have met either. I don't know the soil type based on this picture, but if it is expansive or collapsible soil, that downspout pictured should have termiinated at least 5 feet away from the building.
Re: that 90, turn it around. I'm npt seein any pitch on the gutter. Was there?

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The only reason some people get lost in thought is because it's unfamiliar territory.
- Paul Fix