Was the time travel event mentioned by Bruce Wayne and Barry Allen in "The Flash" (2023) a part of "Zack Snyder's Justice League"?

Question

In The Flash (2023), Bruce Wayne and Barry Allen discuss Barry’s time travel during the final battle of Zack Snyder’s Justice League (2021). As far as I know, this event only happened in Snyder’s version, not in the original Justice League (2017).

Bruce Wayne: So you're saying you went back in time, like in Pozharnov?

Barry Allen: Yeah, like in Pozharnov, except Pozharnov was a second, this time I went back a whole day.

^{- The Flash (2023)}

In Zack Snyder’s Justice League, Barry runs back in time to stop the three Mother Boxes from forming the Unity. Barry mentions that this action sent him a second into the past.

However, Zack Snyder has gone on the record to state that his version of the film isn't canon:

If you needed confirmation straight from the horse’s mouth about the Snyder Cut’s place in the disjointed DCEU, then Snyder obliged during an interview with podcast DC Cinematic Cast, on which he clarified where his lengthy redux stands vis-à-vis the canon he launched with 2013’s Man of Steel and 2016’s Batman v Superman: Dawn of Justice. Potentially upsetting passionate proponents, Zack Snyder’s Justice League—for all its elaborate new bells and whistles—will not be considered canon in the DCEU. Rather, the version released at theaters in 2017, which took shape under the now-controversial stewardship of pinch director Joss Whedon, will remain the acknowledged version of the onscreen superhero tandem.

“It’s interesting, sort of in the DCEU, or whatever it’s become, that that trilogy [Man of Steel, Batman v Superman and Justice League] sort of insulates itself in some ways it becomes, like, it’s its own thing now,” explained Snyder. “I famously said, and it’s true—this isn’t controversial—but you know, this film, my Justice League, is not canon, right? Canon for Warner Bros. is the Joss Whedon version of Justice League, right? That’s—in their mind—that’s canon. And what I’m doing is not, everything I’m doing is not.

^{- Why Zack Snyder’s Justice League Isn’t Canon. Den of Geek}

Does the dialogue between Bruce Wayne and Barry Allen mean that Zack Snyder’s Justice League is now canon in the DCEU? Or were they referring to a different event in Justice League?

Answer 1

Yes, it is.

While Snyder (and Warner Bros.) have maintained the official stance that Zack Snyder's Justice League is only canon to Man of Steel and Batman v Superman (maybe Suicide Squad?), several other DCEU directors, including Patty Jenkins and James Wan, have stated their films are consistent with Snyder's version. Ezra Miller, who was very involved with The Flash's creative process, was also very adamant of the film's connection to Snyder's work.

As for the actual film content, the time travel reference isn't the only Snyder Cut connection. Earlier in the film, Iris alludes to a previous scene exclusive to Zack Snyder's Justice League, where Barry saves her. Also, during the "Chronobowl" scene, where shots from previous DCEU films can be seen, there's a shot of Aquaman angrily pointing at Flash, a shot exclusive to the Snyder Cut.

So it's pretty safe to say Zack Snyder's Justice League is canon to The Flash, and the reference to the time travel scene was a deliberate reference to the film.