That's not true. Preventing jams can actually require more complicated designs. To avoid jams the device should limit the range of motion a device is capable of and deal with dirt and debris. That can require additional parts to stabilize the motion, sealed components, specialized alloys to match thermal expansion, or more complicated motions that clear contaminants.

I think this is a bad analogy made with good intentions. Guns jam because the physical nature of the material is simply degradation. You need to actively fight against it by producing higher precision guns, use more advanced / tougher materials and come up with mechanisms that would reduce the possibility. That's far from simple.