Hi, yes I would think it's very nicely balanced. The doors are attached to the frame by horizontal pivot pin and the triangular sectors are attached to each other by conventional hinges. However I presume there must be a ball joint of some sort between the upper and lower sectors of the door to give the range of movement there. Yes?
Not necessarily, most single garage doors are square and single entrance or internal doors widths are usually less than half the height. A bit of leeway either way is OK because overlap is better for securing the door when closed.