Why are System V message queues conforming POSIX NOT called POSIX message queues?

I know that there are (at least) two types of message queues: System V message queues and POSIX message queue. To my surprise, the man page also says that the **msgget** system call for System V message queues, for example, CONFORMS TO > POSIX.1-2001, POSIX.1-2008, SVr4. Since System V message queques conformed to POSIX, why did the POSIX organization bother to invent so-called POSIX message queues that were different from System V message queues?