If you use the scale diagram for the major scale pattern 1 with the scale degrees notated and color the 3rd and 5th scale degree along with the red colored Root note, then the E shaped barre chord is obvious. Also if you have the 3 scale degrees of the major scale colored in the major scele pattern 1, then you also have an arpeggio note pattern (movable) for that scale pattern. 
All of this became clear last week when I did an exercise of coloring (by hand) the 3 triad notes all over the neck for the 5 CAGED major chords beginning with the C chord:
All Major scale 1 3 5 notes for each of the CAGED major chords
The neck diagram for the G chord shows the notes for the E shaped G barre chord in the 3rd fret clearly visible and you can visualize the G major scale pattern in the same frets.
(Correction: key scale note should be key scale degree)
At first I thought that this was introduced too early since it goes with the grade 4 major scale maestro lessons, but then I remembered that this is useful to know for the lesson on chords in keys in grade 3 module 20. The lesson is called “Chords in Key - Theory-free”, but later it says that you can gain more understanding by looking at the Theory course, which is this lesson.