Bruh, Blue Beetle was already well into production, or mostly finished, when they decided to make the transition into a new universe. So the BB movie is simply just being placed after Flash so the character and his origin will be fully canon in the new universe. It doesn’t mean he‘s the first hero to emerge in that universe either, especially since the trailer references Batman (who will likely have been active for at least 12 or so years if they’re bringing in Damien Wayne), and also the trailer implies Ted Kord was the previous Blue Beetle before Jaime just like in the comics.
Superman Legacy was called the “the true beginning” of the DCU because it’s the first film made specifically for the new universe in mind (Creature Commandos is a cartoon series, and Waller is a TV series). Hell, the film’s events may even be set before the events of the BB film, I mean Captain America 1 mostly took place before Iron Man 1 and 2 and Thor 1.
I’m just baffled so many people can’t seem to get what Gunn meant here. It REALLY wasn’t complicated. The only really unclear thing is Aquaman 2 releasing after Flash, so will Aquaman 2 specify it’s set before the events of Flash, or are they keeping Momoa as Aquaman in the new universe? I mean, they’re keeping Voila Davis as Waller, which annoyingly is somehow confusing people as well (were people this confused when Judi Dench kept playing M in the new James Bond continuity in 2006? …oh wait, they were, *sigh*, seriously why do people think a new continuity means ALL the actors have to change?)