The flashbacks to Eric and Shelly together are pretty rose-tinted and glurgy, yeah, but they're not prosaic third person flashbacks; they're Eric's personal memories. People tend not to recall their dearest loves in flat, dispassionate terms.
Eric has multiple chances to say goodbye to Sarah, but never does, not even after she points this out to him. One look at his face as she walks away from him in the graveyard is enough to see why: he's taken his vengeance now and his rage is spent. He's barely holding it together, and being that real would break him.