John Byrne’s swan song on the title had Superman memorably use kryptonite against the Phantom Zone villains of the Pocket Universe. One minor detail has me scratching my head: when “the worst of the inmates” first get released, one helpfully remarks that the three of them “are free of the Phantom Zone, while our fellow Kryptonian criminals remain trapped there!”
Does anyone know why that got mentioned? Was it meant as a loose end, to be followed up on later?