Then there's this: "It could just be that this specific Apple ID was never changed or edited before. Or if it was, the computer/library may have been authorized for it and still is. It also depends on if this Apple ID was used on this computer itself, or if it was downloaded on another computer or device and re-downloaded in the purchased section of iTunes on the Mac."
iTunes is far too complicated, and far to mysterious. That was a response from an Apple engineer to a problem we've been having with iTunes, iCloud, and iOS/OS X driving our mother-in-law insane.
All of her devices will occasionally, and seemingly out of the blue, demand to 'verify' her, and then pop up the old Apple ID and demand that she use that ID. An email address that she doesn't have access to because it's DEAD, and apparently her old Apple ID isn't. Even after it was changed!
If iTunes is holding on to earlier downloaded items, and that is what is causing this verification jag, then, and this could be earth shaking for Apple: MAKE IT POSSIBLE TO TELL WHAT ACCOUNT 'BOUGHT' IT, AND MAKE IT POSSIBLE TO CHANGE THE ACCOUNT!
As life moves on, people sometimes want to change their IDs, and making that impossible is ridiculous. Having an overly complicated and Rube Goldberg software apparatus like the behemoth that iTunes is, and iCloud seems to be built on, is troubling for the future of the Apple Ecosystem.
I myself really want to change my Apple ID, and I really am fearful of even trying to do it because it's going to start an absolute poop-storm, and it shouldn't be like that!!!