Bowie is quoted in the liner notes of Sound+Vision that he was going to do a "volume 2" to PinUps that would have stuff from the Velvet Underground, Iggy and the Stooges, and a couple of other American bands — so maybe he was doing the "White Light/White Heat" as part of that; maybe to have Pin Ups as a double LP? (Still wouldn't make room for "Ladytron," of course, sadly.)

Don’t think about Young Americans as a makeout album