With my Jo-Jan fletchers when using leftwing for a right hand bow, the bottom hen feather points straight down. On wood arrows, I rotate the nock an eighth turn counter clockwise from the horizontal grain of the arrow and tack it with hot melt. After fletching, I rotate the arrow that eighth turn to orientate the nock to the grain of the arrow. This way the nock index is even with the arrow grain and the feather is turned into the corner of the arrow shelf. I do the opposite for right wings out of left hand bows with wood arrows. I do some with cock feather in as well. I do this so I can the nock as low as possible out of my longbows and still keep my brace height to a minimum.
To answer your question, something else must be going on with spine or tuning or torque. I have seen that kind of wear once before, that was a light spine situation that caused it.