Interesting little tidbit: technically, the first being on Earth-2 to ever learn of the existence of Earth-1 was the Earth-2 Wonder Woman, during a late seventies Martin Pasko-written team-up that paired both Wonder Women together. Of course, Earth-2 Diana was later made to forget it by a magic lasso, but STILL.
Though his BRAVE AND THE BOLD work is more famous, the Alan Brennert/Martin Pasko story about the Earth-2 Wonder Woman was one of the most cornball cool, powerful stories the guy ever wrote.
Sweet Jesus, do I ever, ever, ever hate those nonsense crossovers, like SUPERMAN VS. SPIDER-MAN or TEEN TITANS/X-MEN, that assume that these characters exist on the same earth. Superman exists on Earth-1, whereas Spider-Man exists on Marvel-Earth. It isn't just that, for the most part, these crossovers are badly written. It is that they violate the integrity of Superman and Spider-Man, and insults the intelligence of the reader, by pairing them up on the same earth and not thinking through how such a combined, merged world would look. It ignores real, substantial differences between Marvel-Earth and DC-Earth; you could put the Freedom Fighters on Earth-2 with no real problem, but Marvel-Earth and DC-Earth are vastly different; they even are, as Busiek pointed out in AVENGERS/JLA (the only crossover of this type to ever be done well) of vastly different compositions and sizes.
My assumption has always been that DC was going for the widest possible audience on the "Treasury" editions, as opposed to keeping them fan-centric. My copy of this one, for instance, has a price tag on it from Toys-R-Us, which was not then and is not now known for selling comics. It's entirely possible the Treasuries were early attempts at finding a format that could be marketed to unconventional and non-traditional outlets. With that in mind, of course DC would make everything as "user-friendly" as possible, including using the most familiar version of the chest emblem. "Joe Sixpack and Sally Housecoat" (as Mr Burns would put it) don't care about fidelity to byzantine DC continuity, they just want to see the characters they know.
You're transferring a modern mentality anachronistically onto the comics biz of another (though not too distant) era. Remember, at this time, "Your Friendly Neighborhood Comics Stores" were literally a godsend that, in many ways, saved the industry - this was the era where, if not for STAR WARS comics buoying the company, Marvel would have filed for very real bankruptcy. DAZZLER, the first comic released through direct sales, sold ungodly numbers that a book of its dubious concept and talent shouldn't have made. And Jim Shooter was once quoted as saying for most of his tenure, the three highest selling Marvel books were UNCANNY X-MEN (in the comics stores), AMAZING SPIDER-MAN (on newsstands) and GI JOE (through subscriptions), and on average they sold about as well through different ways.