Pastured Turkey Basics has a much more realistic 200 turkeys per 100 acres recommendation and they are doing it with BBW turkeys. By their very nature, heritage turkeys need more room per turkey than broad breasted turkeys can get by on.
I see a number of the places that say you can do 100 turkeys on one acre but I do not think that is a reasonable number to be able to free range. At least one site says that you need 5 acres to dispose of the droppings that the 100 turkeys produce on that one acre.
Not all acres are created equal and will not be used equally by the turkeys. My turkeys (currently 11 adults) get to free range on 2 acres daily but are closed in a run for the nights for safety. While they use the whole 2 acres throughout the course of the day, they spend most of the day on a 1/2 acre area which contains the best shelter, shade, forage and water.