This is slightly confusing. The route shown in this photo is the Central Buttress (named at the bottom of the photo). Quicksilver begins up and left, at a high point in the snowfield, directly below the notch in the South Ridge. The photo caption seems correct.
Your comment and both captions are all correct. This was the only photo I had of east face, it just happened to be my Central Buttress route layout image. The MP caption probably should also say: "left edge of image" or something, but the "step, notch or bench" is obvious in the shot. Maybe I'll just try to find the image w/o the mark ups.