The Amish/Mennonite raise CX type meat birds. I'm not understanding.
I understand clearly. Amish/Mennonite farmers do not rear poultry as a back yard hobby but as a way to make a profit on both their labor and capital. The Amish/Mennonite community raise chickens so that they can feed and clothe their children, as well as make the payments, and pay the taxes on their farms . Just because the Amish and Mennonites appear to you and me like they are stuck in the 19th Century doesn't mean that an Amish or Mennonite farmer turns his nose up at scientific advancements in agriculture, especially if these advancements improves their bottom line, they can't afford to farm just to make a political statement and when that comes up short fall back on the trust fund that their parents left them.
If the Amish or Mennonites plant heirloom seeds it is because they get good results from these varieties, if that wasn't so they would quickly convert to either Hybrid or GMO seeds. Their refusal to plow with a mule not withstanding.