Now, the X-Men films have something of an obsession with shitting all over The Last Stand (Days Of Future Past erased it from the canon, and Dark Phoenix is an attempt by Last Stand's own writer to fix what went wrong), but this particular line is from X-Men: Apocalypse, a film that's also terrible. It reminds me of how, in the wake of the 1998 American Godzilla, the Japanese Godzilla films would drop in lines about how it wasn't "the real Godzilla" every now and then, as if Japan is somehow magically immune to making hilariously bad movies about giant reptiles.
You can find a slightly more veiled version of this in Jurassic World, in which a Spinosaurus skeleton is demolished by the T-Rex in the end. See, in Jurassic Park III (a film that Jurassic World WISHES it was as good as), the Spinosaurus unceremoniously killed a T-Rex in a fight, and I guess fans were still mad about that? It's the dinosaur park equivalent of losing an argument but then totally winning that same argument when you have it by yourself in the shower later.
Likewise, the latest Halloween felt the need to include an entire expositional conversation among teenagers about how Michael Myers being related to Laurie Strode is just an urban legend, signaling that this wasn't like all of those bad sequels, where that relationship was a crucial plot point. Hey, you know the best way to ensure that the new Halloween isn't a bad sequel? Relaying your information to the audience in a way that isn't just three kids spouting backstory to each other on the street. That's really the problem in a nutshell: The moment you stop your movie to break the fourth wall just to shit on another movie, guess what? You've just made your own movie a little bit shittier.