https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122738
--- Comment #1 from Jan Schultke <janschultke at googlemail dot com> --- See https://stackoverflow.com/q/79823226/5740428 for further discussion. It seems like _Atomic was defined as an alias template primarily to avoid <stdatomic.h> from including <atomic>, but whether intended or not, a consequence of that wording choice is that _Atomic cannot expand to a class template directly. The wording doesn't seem defective to me.
