You won't "see" the grain, but it's there.

When they extrude the plastic, the takeup roller runs faster than the stuff comes out of the extruder, stretching the film at the moment it "freezes" . This aligns the grain, or properties of the film. Little or no stretching occurs along the width of the film. When it shrinks, it's trying to return to it's unstretched state.

Try it for yourself. Cut one wing panel across the roll, and one lengthwise. Cover a left wing with one, and a right wing with another.

Where I learned about it was on patching wings. Grabbing a scrap out of the monokote box, it's hard to tell how it was aligned with the roll. When you get a dippy patch, you know it was sideways.

And yeah, I have been using monokote since before dirt was invented, too. Even before it was "Super".