This doesn't really speed up the save, it just keeps WORD from saving so frequently, which puts the document at risk for losing changes.
No, Steve, you're wrong. It DOES affect the time it takes to manually save the document DRAMATICALLY on the machines where I have tried it (Win 7 & 8). Many minutes is reduced to seconds or fractions of seconds. I have verified this many times.
It seems your answer is based on a theoretical analysis rather than practical tests. Am I right?
I know this does not make sense and is not the way it's supposed to work but it's a fact. No doubt it's an effect of a bug. I just wish MS would take the time to fix it, so that we can spend our time more creatively!