The Amish are heterogenous.
There are progressives and strict traditionalists. I am aware that among the progressives many things including voting are permitted but under the strict traditionalists this is often considered a violation of the congregation's ordnung.
Quoting from the Wikipedia article linked below:
Because the Amish have no central church government, each assembly is
autonomous and is its own governing authority. Thus, every local church
maintains an individual set of rules, adhering to its own Ordnung, which
may vary from district to district as each community administers its
You conveniently ignored the fact that the quotation which you quoted implied that there are congregations which do not allow it to be an individual decision. The quote alleged that "most congregations" allow individual decisions but that means that there are some who do not allow it.