General :: Shutdown Works And Init 0 Doesn't So How Are They Different

When I bring down a certain machine with some nfs mounts using init 0, it hangs forever while trying to bring down the mounts, but if I bring it down using halt -p (which I've read just calls shutdown if I'm in init 3), it comes down in a timely manner. I've also read that shutdown still calls all the rc.d kill scripts just like init 0, so what is actually the difference between them? Is it this:

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All processes are first notified that the system is going down by the signal SIGTERM?Does init not do that? I'm not trying to directly troubleshoot why NFS makes me hang with init 0 at this point, just wondering why shutdown works whereas init 0 doesn't.