On Mon, 25 Nov 2019 at 23:11, Billy O'Neal (VC LIBS) via Lib
<lib_at_[hidden]> wrote:
>
> This was explicitly brought up for review in LWG and if I recall correctly the result was that we were OK with this inconsistency since that feature test macro had already been shipping in implementation(s).

Vague recollections are not worth much to me. This is at
http://wiki.edg.com/bin/view/Wg21belfast/LWGThursdayAfternoon

"Discussion about inconsistency of __cpp_lib_array_constexpr vs
__cpp_lib_constexpr_*header*
Consistency is nice, but not necessary. No consensus to change. "

Granted, those notes aren't worth much to me either. :) They do seem
to indicate that LWG discussed this
very matter. I still don't see a very convincing reason to deviate
from the policy, considering Richard's correct
remark that the existing feature-testing macro can continue to ship.