Of course, Valve could have been making it all up as they went along and not actually developed the Combine style till after HL1 was released.
This has been my impression all along - at least judging by Raising the Bar. I believe they started almost from the scratch after hl1, as regards the story, so we didn't see Combine style in hl1 because they had never even thought about the story that far. But I don't know their official statement on this.