Why it is allowed to initialize static variable with non const here?

Question

I was reading this. The first answer by @Andrei T says that

A \"large\" object is never a constant expression in C, even if the object is declared a

Answer 1

This seems to be a gcc speciality. Compiling with -std=c89 or -pedantic reports the error.

Since in all C standards this is a constraint violation, not giving a diagnostic for that case makes gcc without one of the -std=c?? options a non-conforming compiler.