"Moderato con grazia" is the last A section that returns to the themes set in A. After recapitulating the "walking" themes, Gershwin overlays the slow blues theme from section B in the final "Grandioso".
"Moderato con grazia" is the final A section that revisits the motifs introduced in A, after reiterating the "strolling" themes. Gershwin then superimposes the slow blues theme from section B onto the grand finale's "Grandioso".