See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2128r6.pdf

Did we ever discuss this in a liaison group meeting?

While the paper is not proposing to add multi-dimensional subscripting
for raw arrays, it is doing a land grab on what that syntax means.
I got the impression that some WG14 members have different ideas
for that sort of a syntax, based on earlier email discussions.