I think the distinction is that getting something going with enough velocity to escape the gravity well of the Sun, and in a vector the points it towards another star's gravity well is different than getting living representatives from a civilization around one star to another.
Philosophically, even an Ark ship, with technology capable of sustaining a population of humans for a million years wouldn't fit the bill since I'd argue that by the time the descendants arrive they:
a) would probably not be the same species anymore, having evolved over thousands of generations for ship life
b) wouldn't be the same civilization anymore, having developed their own micro-civilization in the intervening years -- they'd no longer be representatives from their home civilization...any more than I as an American can be a representative for the European civilizations I am descended from when I travel to Asia
c) their home population and civilization will have evolved and diverged from the Ark's population and civilization regardless of the Ark's conditions. Even if the population on the Ark was put into some kind of suspended animation for the length of the trip (preserving the both the original species and civilization) they'd be representing a species and civilization that no longer existed
Philosophically, even an Ark ship, with technology capable of sustaining a population of humans for a million years wouldn't fit the bill since I'd argue that by the time the descendants arrive they:
a) would probably not be the same species anymore, having evolved over thousands of generations for ship life
b) wouldn't be the same civilization anymore, having developed their own micro-civilization in the intervening years -- they'd no longer be representatives from their home civilization...any more than I as an American can be a representative for the European civilizations I am descended from when I travel to Asia
c) their home population and civilization will have evolved and diverged from the Ark's population and civilization regardless of the Ark's conditions. Even if the population on the Ark was put into some kind of suspended animation for the length of the trip (preserving the both the original species and civilization) they'd be representing a species and civilization that no longer existed