On the other hand, different species do "warp" in rather different ways. It wouldn't surprise me at all if warp were just a catchall term for all the possible methods of FTL travel - and methods that visibly differ from the things called warp are impossible.
Say, "wormhole" is another vague concept that has been associated with at least three different VFX, each of which also differed conceptually on how a spacecraft would pass through (ST:TMP, "The Price", DS9). And our heroes agree that wormhole is not a valid FTL travel method, until the Celestial Temple comes along. Quite possibly, it's all "warp" and "wormholes" and nothing else can exist without being absorbed into one category or the other.