However I suspect the whole "motivic development" is that all the dramatic and seemingly sudden dramatic shifts in the variations/contrasting sections of the piece are based on the same motif of the riff underlying the song. As well as some of the instrumental lines that exist more for harmonies and the vocal lines share similar motive to the riff.
This is how Gentle Giant can do multiple section and sudden shifts in mood while still sounding like it belongs to the song because each section has a
In a way it's a clever synthesis of rock and roll guitar rock "riff based" music with classical techniques. Using that repeating riff as the theme to be developed and the harmonic accompaniment and contrasting sections are based on that theme.
Yeah I'll upgrade it to a 13/15 Hex D