The side with the grade stamps is intended to be installed down to allow for the stamps to be visible from an unfinished lower level. Installing the panels this way allows for material verification and inspection from below (when carpet or tile may be covering the top side) and ensures that the tongue and groove joints will properly align and avoid causing an uneven lip at the panel edges.
Also, by installing the stamps down, the rougher side of the panels is kept upward which helps with worker traction on the jobsite.
However,structurally there is no difference in how the panel will perform whether the side with the grade stamps is installed up or down.
For Weyerhaeuser Edge Gold, the down pores must be faced down in order for the self-draining system to work correctly: meaning that when the OSB Edge Gold is placed on the floor, the pores should not be seen.