Re: Sorry, I still don't get it...
Thanks guys - The Melbourne pit lane parallels the start/finish straight, so no advantage in distance. I think what I was missing was that, of course Vettel was in front after Hamiltons pit-stop, so it wasn't a matter of over (under) taking, just not losing all of his 20s temporary "lead".
Plus going full speed to open the gap in the 3rd sector before diving into the pit lane would help, though I'm not suggesting Vettel gamed the VSC that way. Or even entered/exited the pits at race speeds.
I guess Hamilton could have sped up at the start of the following sector 1 and then slowed and blocked Vettel from passing, but that would have technically been "overtaking during a VSC".