No two horses have the same head shape.
There are basic differences, such as long narrow heads, short wide heads, heads that are wide at the top but narrow at the muzzle, etc.
There are also differing ear shapes - short 'Pony' ears that are bulbous at the rear, ears that are long from Poll to Ear Base, etc.
There are differing Polls too - wide Polls, narrow Polls, Polls that are still rising from the neck and Polls that are flat at that point, etc.
It is impossible to create just ONE Headpiece that is truly 'Anatomical', in all aspects, for all horses, though many Manufacturers do just that.