STeve, I'm not so sure.
1. We expect technology to be perfect, and are surprised when it is not. I've seen people argue over where a trail was, based upon GPS, where the difference was a few feet. No understanding of accuracy.
2. There are certain things that crop up in technical fields unexpectedly. Sometimes referred to as the "ghost in the machine". Extremely hard to track down or explain.
Remember that these maps were generated from aerial photographs. One artifact that may have existed were shadows. For example, a shadow line may exist at 8-9am that might approximate this, and the software might not interpret it correctly, or even know what to do with it. Also, the software allows one to adjust the "shading", and it might interpret things funny.
3. mapmakers usually deliberately place "errors" on their maps, as a watermark to protect their copyright. These are things that will not effect use.
I believe we are talking about #2, here. We all know that there is nothing on the ground where that line is. Such shading usually refers on topos to vegetation, and there clearly is none.
I recall one map system that allowed you to run/stop the motion of the sun, with the shadows running across the terrain from dawn to dusk.
Also, the pictures used are spliced together by the software, and there may be artifacts of the pictures. For example, using the G4 maps, when I switch to "satellite view", and move a little out, there is an artifactual vertical line created between photos at the west base of Whitney.
I imagine this drives mapmakers crazy.
