I think you might kick yourself for not QT later on, expecially if you're a fish store junkie -buying fish from all over.
IME Petland does not keep their pH nearly that high although Petsmart might since they automaticly change their water 3 times a day with a mix of tap water and filtered water (my brother works at a PetSmart and Petland doesnt change their water enough- no one does- to maintain such a high pH in retail tanks. Retail tanks are normally low in pH IME). That's kinda high pH IMO for tetras, but to each their own. If the fish are wild caught, which PetSmart's may not be (they actually are very into keeping thing cultured) and thus the lack of death.
Wild fish are much more fragile and harder to care for than cative stock. Cative raised stock, like the ones from Matt, are far more likely to survive in another aquarium and IMO shouldn't be added into the equation. Any fish acclimated for that long in captivity will be hardier, regardless of it's inherit past.
Also, you may want to take into account that neons and cardinals are not hard for everyone to keep. I've kept cards years ago, in subpar conditions, and didn't have issues until I lost interest in the tank and killed them. You may want to look into you pH and see if you can't bring it down a little. The acclimation shock may actually hard them in their very specific case and therefore you;re getting favorable results with the "dump" method.
Like I said, I would not dismiss the idea of QT. The time you take it for granted is the time you get wild stock infested with who-knows-what that stresses the entire tank. Vigilant- yes. Too gung-ho.... maybe.
Just playing a little devil's advocate here too. :P