I have a bad memory, so I would not remember this happening. Do you have an example?
Also: why would they do that? If they already have the footage, and it is 'impressive' (for the trailer), why NOT put it in the movie?
Usually I avoid trailers. It's marketing, spoilers, trying to sell you the movie. For me, they might be clever, but that's all. The Payback trailer is clever because it has no dialog... https://youtu.be/ji6aaZRACew
Drama behind the scenes on Payback saw the director fired by the studio and replaced, a completely new ending written and shot.
Normally when studios mess with the writing, the film suffers, but not in this case. The theatrical release of Payback is better than the "director's cut" released on video a few years later. The director's cut has a boring ending, just generic gun fights and a mess of scenes. The theatrical release has a good twist, more substance and style.
“Sometimes we’ll start on a trailer before they’ve even started filming,” Gritton says. “We just break down the script. Then we’ll get dailies—literally everything they’ve shot, hours and hours.” The dailies are covered in ghostly watermarks and stamped with the producer’s and house’s name for security’s sake, making them nearly unwatchable and of no real use to pirates. Theoretically.
Given the extraordinary and time-consuming process of CGI, sometimes green screens, motion capture dots on actor’s faces, maybe a cardboard cutout where a dragon will eventually go are still visible in these early cuts. “We’ll pick what we think are the best takes,” Gritton says. “The majority of the time it’s not what ends up in the film, which is why you see stuff in the trailer that you may not recognize later.”
As a recent example of this, there are several trailers for Baby Driver where we hear Doc describe Baby as "Young Mozart in a go-kart," [1] but this line is never heard spoken in the film (though we do see it written on one of Baby's cassette tapes).
Here's an article with some examples for you though.
http://www.denofgeek.com/uk/movies/movies/47071/41-trailer-s...