Yup, a string pot or a string encoder would normally be a simple, reliable feedback mechanism.
If the designer can be assured that it will never be moved other than by this control mechanism, a lot of my concerns go away. I have memories of a safety-critical system I worked on that used encoders for positioning, and all the trouble we had to go to to ensure that if someone messed with the positions while the power was off, we would always behave correctly. An awful lot of engineering went into making that fail-safe.