There is also symmetry in the scene with Ennis in the alley when compared with Ennis leaving the Twist family house in Lightning Flat.
In both scenes, Ennis isl alone and missing Jack, and in both scenes Jack has been subliminally suggested:
In the alley scene, we see a figure in the clouds that suggests Jack driving away.
As Ennis leaves the Twist house in Lightning Flat, if you look very carefully, Jack's name is spelled out subliminally across the screen.
The J is in the reflection of the truck window.
The A is the triangular dormer on the house.
The C is in the cloud over the house.
The K is buried and trails off in the angular mass of trees to the right.