The Russo brothers saying "these are not teasers or trailers" might lead some to believe these scenes are not in the actual movie. They might be shot specifically for trailers that serve as prologues to the events of Avengers: Doomsday, similar to how the post-credit scene for
Captain America: The Winter Soldier was a prologue for
Avengers: Age of Ultron, or how Captain Marvel's presence in
Avengers: Endgame is explained in the post-credit scene for her film. Now that theory might be true for some of these moments, particularly the post-credit scenes of
Thunderbolts* and
The Fantastic Four: First Steps, which were essentially the first teaser trailers for
Doomsday, but it could not be all of them, as
The Fantastic Four meeting both the Wakandans and Namor will likely have to be part of the movie since that will be too big a scene to gloss over.
Source.