Never liked this episode. Seems to undermine the idea of 'truly' alien species coming to understanding. Once their ultimate roots are identical, so what?
Doesn't have any particular implications for evolution, though, not sure why people are saying that.
Well, there are still many "truly alien" species out there, since only the humanoid form was the result of the seeding program, not intelligence in general. And it's possible, even likely, that some humanoid aliens in Trek are the result of convergent evolution rather than the seeding program.
In the end, it's just Trek's attempt to hand wave all the human rubber-forehead aliens, nothing more.