You have managed to take the wrong end of the stick very firmly here. The point isn't to say that EP1 has more plot than HL2 had, far from it. Rather the point is to show how EP1 has advanced and expanded the story.
Also for those who consider the opening sequence to be a cop-out, I'd suggest spending a little time chatting with a Vortigaunt in HL2. While you do have to wade through a bit of chaff a lot of what happens in that opening is directly hinted at by various responses.
If anything that is perhaps the biggest revealation in EP1, the Vortigaunts are shifting from being the slaves in Half Life into an unfettered force in their own right. Quite possibly the real long term salvation for humanity as the means to manage or close the portals the Combine use.
It is going to be fun to find out.