I don't get it, you are still applying the force in the same direction. I mean if you rotate the 'wrong' picture by 90 degrees you will see that they are both the same thing
In the "Right" photo, the glue is at the top of the image. In the "Wrong" photo, it is at the top of the image too.
The wrong movement detaches the glue from the center of the pad to the edge. The right one detaches it from the right side to the left side of the glue bar. Both directions are orthogonal.
I love how this one comment thread and its replies highlights the importance of being a good visual communicator. One bad image, one bunch of confusion.
You can’t really tell in the photo, but I believe that in the “correct” picture on the left, the adhesive is on the bottom near the thumb, or the side opposite to that.
If the adhesive edge was an axis, the article is saying to peel along that axis, whereas more typically folks peel perpendicular to the adhesive axis, causing the post-it to curl up and out from wherever it is placed.
The green and red post-its have the same orientation, the adhesive is on the top for both. So when you peel the green one off, you're peeling the adhesive right-to-left across it, whereas when you peel the red one off, you're peeling it from bottom to top almost all at once.
The wrong movement detaches the glue from the center of the pad to the edge. The right one detaches it from the right side to the left side of the glue bar. Both directions are orthogonal.