What is exactly an "invalid conversion specification"?

As per C11, chapter §7.21.6.1, P9

If a conversion specification is invalid, the behavior is undefined.²⁸²⁾ If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined.

Till time, my understanding was, for

  char str [] = "Sourav";

• A statement like printf("%S", str); belong to the first sentence, there exist no CS as %S (UPPERCASE)
• A statement like printf("%d", str); belongs to the second sentence (mismatch between CS and argument type, but the %d is not an "invalid" CS, anyway)

until advised otherwise by a recent comment thread.

Is my understanding wrong? Can the second statement also be categorized as "invalid" (PS- not "wrong") conversion specifier?

_{Update: The answer and the comment thread is deleted, here's a snap for <10K users.}