wfpeterson can do whatever he likes to modify things the way he wants them to be. That's no skin off my back.
For me, Fallout is primarily story-driven and all games (mostly) follow a strong narrative. I think the OP would agree with me. It is not enough to satisfy this narrative, therefore if TTW is going to be successful in uniting the player's experiences as both the LW and The Courier that complete freedom be given to the player in traveling back and forth between the two wastelands. I think we can all agree on this point.
I want to explain further, because what TTW does in synthesizing the story-driven content of both games is really in effect to create a new game. In Fallout 3, you don't complain that content from Broken Steel is accessible only after the main questline is completed; it's how the game is played. By the same token, if in TTW you aren't able to travel to NV until certain time-sensitive issues in the capitol wasteland are resolved (which have been discussed), you shouldn't really complain either. It's how the game is structured.
If you don't care about narrative and want to play Fallout because of VATS and explosions, then fine. If instead you disregard the intent of TTW, if in effect you continue to insist on looking at Fallout 3 and Fallout NV as separate games, then it's easy to understand why you should think that the player should be allowed to travel between the two wastelands without restriction. The narrative is already cocked-up between them and so what does it matter if a train ride comes in between any of the main plot points of Fallout 3.
As an aside, it's interesting that this same confusion over what TTW is and what it does has led to some questions in the past regarding which game should be launched after installation and which data directory should be used in order to okay it.