I tend to think there were others such as Seventh Day Adventists that resisted in large enough numbers to be identified as a group.
However, other than JWs, what other sizeable group of people can be pointed to as having had a choice to remain "free" by bowing down and worshiping Hitler, or refusing and being sent to concentrations camps that chose the camps?
I’ve studied the persecution of the church for 30 yrs. Hitler had a whole list of Christian denominations he outlawed and persecuted.