In my puny experience, I find that “making the object appear to emit light” and “providing the light that the object would (in the real world…) emit” are actually two entirely different things. The strategy adopted by this tutorial makes the tubes “literally, THE source of the light.” But I suspect that an equally convincing effect could have been achieved by taking advantage of the fact that “a CG light source” can be right there in plain view and not be seen.