True, the terms are not equivalent but they overlap.

From the same article:

Geographically, Pennsylvania Dutch are largely found in the Pennsylvania Dutch Country and Ohio Amish Country. The main division among Pennsylvania Dutch is that between sectarians (those belonging to the Old Order Mennonite, Amish or related groups) and nonsectarians, sometimes colloquially referred to as ″Church Dutch″ or ″Fancy Dutch″.[12]

and:

Although speakers of Pennsylvania Dutch can be found among both sectarians and nonsectarians, most speakers belong to the Old Order Amish and Old Order Mennonites. Nearly all Amish and Mennonites are naturally bilingual, speaking both Pennsylvania Dutch and English natively.[9]