Spacetime is by no means a flat plane with a fixed notion of distance. It doesn't matter how far apart points A and B were, warp drive simply makes the necessary corrections to the universe such that there is a shorter path to get there. For example, we can see galaxies which are 46 billion light years away. Those stars "warped" to their current locations in a mere 13 billion years. Nothing FTL about that. The question isn't whether spacetime is malleable, it's whether there is any practical way of doing it.