DX ∪ UX = U ∧ DX ∩ UX = ∅
User Experience is primarily concerned about guiding the user to a desired outcome in the most optimal way, optimizing for time and margin of error. That's why the term journey is heavily used within the context of UX design. Developer Experience on the other hand, is not about guiding the user, but designing the right abstractions and choosing what part of the system complexity to expose to the developer.