Front Sight Index Line / Mechanical Zero?

I've noticed that the index line on the front sight drum and front sight block have a noticeable variance between different countries of origin; for example on my Hungarians the line on the drum matches up with the front sight being slightly off-center to the left which turns out being zero for me. However, on my Romanians, it is just centered on the drum, resulting in the line being offset to left for my zero. Does anyone have any further information on this (which countries of origin have arbitrary marks versus what appears to be true mechanical zero as on my Hungarians)? Thanks.