"Мне до лампочки": Cold War Propaganda, Language Learning, and Light Bulbs

In learning a language, it's often the case that we encounter new idioms or expressions that make little sense without historical background or further context. (E.g. this expression, and for a more extreme example, this episode of Star Trek: TNG.) Such was the case when I was learning Russian a few years ago, and I happened upon the expression "(это) мне до лампочки", lit. "it's just like the light bulb to me". Figuratively, this is taken to mean that the person does not care much about the thing to which he is referring. This idiom is apparently relatively new, taking hold within the past century or so, and two of my professors have given me rather differing information about the etymology of this expression.

1. The first professor, an American, explained to me that during one of the many Soviet industrialisation programmes, there was a drive to provide modern lighting systems to the general populace. However, because of inadequacies in the Soviet system, this programme took far longer to complete than originally envisioned, so the phrase "мне до лампочки" entered Russian vernacular as an expression describing something pointless or worthless.
2. In a later encounter, a second professor, a Russian, refuted the first professor's claim as American propaganda leftover from the Cold War. According to him, the true origin of the phrase is the following: In earlier times, miners often fastened mining lamps to themselves via straps or harnesses. In Russia, one method of wearing the lamp involved fastening the lamp near one's crotch. Thus, "мне до лампочки" actually arose as a miners' euphemism for a more vulgar phrase, later being adopted by the Russian-speaking population as a whole.

While both explanations are plausible, a quick Google search for "мне до лампочки этимология [etymology]" lends more support to the latter theory. This naturally leads to the question: supposing the first explanation was indeed false, how and why did it arise? This may be hard to determine without much more research, but it seems clear that even in fields such as etymology, political and cultural biases can surface.