I think they mean that the holes should be ether vertical or horizontal (timed / indexed)
to look right and to direct gas the in same direction to prevent odd thrust vectors that
could effect accuracy.
The breaks with the holes/slots on the side need to be horizontal with the action for the same reason. For example= if a rifle strings the group horizontal it usually means that the stock
is allowing the action and barrel to move the same way, This is why we bed rifles to prevent
this movement. and if you have a break that is not timed/indexed it can also cause a harmonic
imbalance because the action is held to the stock vertically and the loading will be uneven
and may cause poor accuracy.
Just my opinion.
J E CUSTOM