Every well-arranged sitting room has at least one seat that can move. Fixed seating - a corner sofa, a built-in bench, a wall-run - organises a room efficiently but locks everyone into the same orientation, and conversation between people sitting side by side along a wall is oddly difficult. A single chair that can be turned solves it, because the person in it can face whoever is speaking.
That is why this armchair is built taller in the back than the sofa. A chair meant for conversation should hold you upright; a sofa meant for relaxing should let you sink. Making them the same height would suit one of those uses and not the other.
The craft question is keeping the two pieces looking like a pair despite those differences. Our master Indian artisans work the same crest, the same arm scroll and the same buttoning grid on both, and let the proportions differ - so the eye reads them as a set while the body notices they are not.