damdao

While it is true that not everybody has the obligation to know what neidan is, mainly because it is, perhaps, the less spread of the spiritual systems, the misinformation that qigong and neidan are the same has to be stopped. We know that qigong is a modern umbrella term for several traditional practices more or less adapted (and sometimes diluted). Practices like yangsheng (not to be confused with yangshen), daoyin, neigong (either martial or medical), etc. were fused in one model: qigong. But neidan was not part of this process, although some neidan methods can be found from time to time in qigong systems. Besides, there is the difference in method and energy used (already explained by Antares).

Chapter 1 of DDJ does not speaks about Xuanxue but about Xuan. Xuanxue is a philosophical movement, as Xingshen has pointed out. And maybe your translation is a bit misleading.