Valve has a pretty well-established history of promising one thing and delivering another.
Not sure what exactly you are getting at here...
They released a lot of cool bits of scenes from HL2 that never made it into the final version, but that doesn't seem to happen with the episodes because they are developed over a relatively short amount of time.
In fact, that first shot of Ep1 with Dog digging the player out of rubble seems to look better in real-time on my computer than in the trailer which was released long before the game was released.
HL2 ep1 is about 5 hours long if you rush through it and don't bother with the commentary.
As I recall, that's about how long they said it was, since they are quite clear in saying that the games are episodic.
I actually haven't ever encountered Valve doing completely blatant bullshots and calling them real.
Just about every bit of media they release is from a test build of the game at some stage or another, and I think we can be sure that that scene with the GMan is, in fact, very similar to the scene with the GMan that we will see. (Though the camera stuff seems a bit odd, so it may have been an in-game render to fit the trailer better. Still, the shadows must have been enhanced for the real-time stuff because they make that scene come to life and without them it would not work).
The actual videos of TF2 look very much like that TF2 teaser released earlier, so my belief that that was completely fake and propped up by engine features that don't happen in real time has been quelled.
The animations aren't as convenient and there aren't guys hitting themselves on the head with shovels (of course), but other than that I think - as usual - the in-game footage they've shown looks better than the teaser.