It may have always been part of the plan, but it’s entirely possible that Joss Whedon captured the moment during Justice League’s extensive reshoot process.
Though it was part of Snyder’s plan for the showdown against Steppenwolf, it remains unclear which director actually brought the sequence to life.
Of course, Jay Oliva’s confirmation that the freeze breath was always part of Zack Snyder’s vision does not fully explain the incorporation of the ability into the movie.
Considering how little we actually know about the earliest incarnations of Justice League before Warner Bros. decided to make some massive changes to the film, we will have to wait and see if we ever get more context to flesh this story out.