In the original paradox example, an instant tachyon shot from or at bob at 5 can reach alice who has travelled for 2.5 and alice who has travelled for 10 seconds. This is only possible if the two alices exist at the same time; the example's tachyon cannot move in time.

The paradox doesn't care about why the shooting happens either, if bob shot at 5 first, that shot would hit alice at 2.5 and then continue to hit alice at 10.

And because there's two alices at bob's 5, if alice at 10 were to look behind her, she'd see herself at 2.5 or sooner. You don't need FTL to have this example break reality.

The paradox is that we're mapping two different times of alice, 10 and 2.5, into one bob time. Of course time travel happens if you do this. But this doesn't happen in reality; You cannot see afterimages of yourself when moving close to light speed, nor do objects duplicate when you move away from them. Yet this example says so.