Doesn't the rest of the RAW information kick-in at some stage?
It's not just the demosaicing that happens while converting raw to a displayable image, as far as I know.
There is also the various algorithms used for such - ufraw has, like, 4 or 5 of them, with distinct advantages for each.
Then you got the actual conversion curve. Each sensor maker may have a far from linear light response curve, which means a correction might have to be applied otherwise you get the equivalent of a weird monitor gamma.
And then of course you get the colour temp information to be considered. That's another curve modifying factor.
None of those apply to the tiff case, where the image is simply stored in an already "decoded", visible fashion.
Did I completely miss your concern or does the above rambling make any sense?