I'm glad to see research on Maydole published!  But I don't believe the
adz eye was designed to solve the problem of the head flying off. 
Rather, I'm fairly certain the design reduced handle breakage due to
pulling nails with the claw.  I have earlier blacksmith made claw
hammers that show other attempts to reduce such breakage.  One in
particular increased the length of the eye to put more "meat" in that
end of the handle.  In my experience, the greatest risk of flying hammer
heads is handle breakage. 

Mike in Woodland