Wow, this is a nice discussion, way different than what I thought from the title. From my experience, I don't think they are faking, they basically just playing any old thing cuz they don't know the actual. Most of your small churches don't really care if a person plays right, they just want a musician. Then, when they get a visit from a church who's musicians play correctly, they want to start complaining.
I've played with some of the best and worst musicians in my part of the world. I've found that it's the more mature person who will do what is necessary to make everything "gel" and get through the service. Many times, I had to be that person. I had to swallow my pride and go along so that spirit keeps moving.