Regarding Fig. 4: You can't create that kind of selection in Blender—unless you use a script. But that's not a valid selection. If you switch to polygon selection mode afterward, your selection will disappear. To verify this, just try repeating the same steps manually. Select all the edges of the cylinder’s cap, making sure not to select the polygon inside those edges. I see what you mean. Exactly—in Blender, selecting all boundary edges of a polygon automatically selects the face itself. This often leads to confusion when applying operators, as the tool targets the entire face/island rather than just the edges. It's always particularly confusing and frustrating for artists transitioning to Blender from other 3D modeling packages, as they expect edge selections to remain isolated.