[Ronbo]

No idea why the outside needed it. On the side bolts (since they are bolts) you would want a slight inside chamfer. This is to provide clearance for the concave transition from the bolt head to the shank. (a sharp 90 deg transition is a potential fracture point) Perhaps the machined pads on the block needed it at some time? (mine were larger than the washers)

Most washers have a "sharp" side caused by the stamping process, this should always be installed away from the bolt head.

In 99.9999% of all cases this is not a big deal except for space shuttles and cars that hammer the heck out of their drivetrains. Putting the washer on wrong won't make your fender fall off, but it's a good habit to have.