I don't follow? The requirements in 334 pertain to the wiring method in the sleeve. The requirements in 300 pertain to the sleeve itself. They don't conflict.
Article 300 General Requirements for Wiring Methods and Materials. Completeness plus mechanical and electrical continuity are excepted. What section covers securement and support of a raceway physical-protection sleeve?
300.11(A)? I suppose, but I infer that section to mean raceways used in wiring methods... and we're back to intent.
If we look at it your way, how are we supposed to weigh the requirements of 300.11(B).
300.11(C) is what you are saying about the cable supporting the protection sleeve... and I agree with that.