The net pressure force points along the surface normal, not along the incoming beam, because the surface can only push back perpendicular to itself. At oblique incidence the delivered momentum also picks up a cosine factor from the projected area. This direction rule holds for ideal flat surfaces with stated orientation; real surfaces are curved, rough, and partially absorbing, and the angle and power are measured quantities with error.
A radiation pressure label includes its finite direction convention. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Pressure direction follows the surface normal
The finite direction label is part of the checked pressure surface.
direction=normal
Opposite direction is not the same claim
The engine rejects a raw opposite-direction pressure check.