It was a little bit on purpose TBH, it leaves some room for though, and broadens the scope or definition of alien life.

We already know organic compounds can survive in space on astroids and comets, and we know these compounds can survive impact with planetary bodies.

What’s to say these same comets have not impacted other planetary bodies in our galaxy, or have traveled between galaxies in our Universe.

Timescales would make it impossible to know if two species on two planetary bodies would evolve at the same time.