Using the Expansion-option in the Face-tool, you can expand a shape based on face-by-face.
Faces rotete around one of their edges.
Depending on the order of expanding faces, the resulting form varies.
You CANNOT expand a face if the face's rotating axis is NOT connected to another face.
In the avobe case, the face: ABFE can't be expanded around the edge: AE.
Because the edge: AE is not connected to any face.
Also you CANNOT pack the selected face if the face is expanded around some axis edge, which is the edge of another expanded face.
In the above case, the face: ABFE cannot be packed because it has been expanded around the edge FE and the face FGEH has also been expanded.
While the face FGEH and the HGCD can be packed.
But the ABFE can be packed if the FGEH is packed.