The peak of this crest is the highest point on the sofa and it is also the single most vulnerable piece of carving on it, so the timber behind the design is chosen before the design is drawn on it.
A peak means the carving converges toward a point, and at that point the grain of any board must run somewhere - if it runs across, the tip is short grain and will break at the first knock; if it runs vertically, the tip is strong but the wide base of the triangle then has grain running out at both lower corners.
So the crest is built as three pieces: a central vertical member carrying the peak with its grain running up through the point, and two side sections with their grain following the slope of each shoulder. The joints between them fall along the lines of the carved scrolls, so the pattern covers them.
Every part of the crest therefore has long grain running in the direction that part needs it. It is the same principle that lets a stone mason build an arch out of separate blocks - the shape is achieved by assembly rather than by asking one piece to do everything.