Every leaf does not produce a new plant. Last summer I made 5 leaf cuttings from young plants with leaves about inch across. Two of these leaves produced plantlets, which were potted up and are doing well. Two produced only roots and were eventually discarded. The 5th leaf did not produce either roots or a plantlet.
Plants grown directly from seed are always or nearly always single-headed.
Plants grown from leaf cutting sometimes have more than one growing points. Older plants with stems can be beheaded and they then develop new growing points. These new growths can be removed and rooted to produce new plants. Last fall I beheaded the plant that won first place in its class at the Midwest conference in 1998 and it now has two new growing points. I will soon be removing these new growths and rooting them to produce new plants.