How would that work? It would need to depend on the grammar of surrounding C code. This directive isn't limited to variable initialisers. You can use it anywhere. So e.g. you can use it inside structure declaration, or between "int main()" and "{". etc. etc. Those will generate errors in subsequent phases, but during preprocessing the compiler doesn't know about it. Then there is also just that:
int main () {
return
#embed "file.bin"
;
}