Well, there are several "kinds" of wormholes. In one, the distance really is 3 ticks, in every way that matters, and the fact that there's also a 10-tick path (which used to be the shortest path before the wormhole) means nothing, as there are an infinity of circuitous paths. But that's not this kind of wormhole.
To see the problem, imagine 2 wormholes, A and B, each with widely separated endpoints. In my reference frame, the endpoints A1 and A2 are stationary - I'm standing by A1 and can send a message instantly to A2. The endpoints B1 and B2 are stationary relative to one another, but are moving close to c relative to A. In B's reference frame, my message goes back in time.
If my message gets relayed A1-A2-B2-B1 just as the endpoints pass, I'll get it before I send it. In my reference frame, A1-A2 is instant, but B2-B1 goes back in time. In B's reference frame, A1-A2 goes back in time, and B2-B1 is instant. Either way, it's a causal mess.
A simpler example: you can get a straightforward time machine simply by accelerating one end of a wormhole up to relativistic speed for a few years, and then bringing it back, parking it at rest near the other end. Like the twin who visits a distant star and returns, one end will be "younger" than the other. Now the wormhole moves you back (or forward) in time by a few years when you traverse it.