"Data portability" is vague so that the law is stable and flexible. As a comparison, "drivers need to adapt driving speed to weather conditions" is equally vague. It would simply be infeasible to publish an hourly speed limit chart based on rain, fog, snow, etc. It is the responsibility of driving instructors to raise awareness on reasons to adapt the speed. Drivers need to then interpret that clause to their situation.
Similarly, it is up to industry -- either via standardization bodies or courts -- to clarify what exactly is "data portability".
