I think it is the aspect of behavior and information control that makes them a cult.
Sure, they're not as bad as the worst cults. If I cut my finger, no one says "that's not a cut, the finger is still attached." It's not as bad as it can be, but it's still a cut. The WTS can be a cult without being murderous brutes. Although the line might be a bit blurry when it comes to denying blood transfusions.