Of course, it's comics so it could just as easily be another Riverdale canon they're colliding with that just looks like the show and is exactly like it except the couple things they changed....
There's like five different characters in marvel comics from different "the real world" universes that are all just 'our world except so-and-so comes from there'. And that's a tame example of that kind of thing.
So yeah, it could certainly be a "crossover without ever actually crossing over" like with marvel vs DC or whatever