Just to clarify one point (because there are some people who'd never forgive me if I left it unsaid) while Julius Schwartz was the editor on the Superman books, Superboy was edited by a fellow named Murray Boltinoff.
Among Boltinoff's quirks was being very anti-continuity even before "continuity" was such a widely used term in comics; he didn't like references to previous stories in his comics, or anything that only hardcore fans would get. So he was probably against an explanation like this being done at all, and its weirdness may reflect his disdain. "Yeah, yeah, just say the youth potion was sent by an alien...hey, how should I know why he does it, that's your job...leave me alone!"
It'd be nice if folks could include issue numbers or similar identifying features when posting scans. Someone wrote this, and whether we praise it or scorn it, that person's name should be acknowledged. I'd like to be able to look it up, but I don't know what issue this is. I have a strong suspicion the above was scripted by a comics writer I like a lot...but I'd have to say this wasn't his shining moment...