The term "astral plane" is older than D&D, and I would assume they took it from the more general usage, not the specific usage in D&D. https://en.wikipedia.org/wiki/Astral_plane
I’ve met several of the Unicode standard committee - They’re nerds. The kind of nerds for whom “Astral Plane” is a multilayered joke. It’s not not about the general usage, but nor is it not about the D&D term.
