Re: Sorry, I still don't get it...
It's not at all about being faster than under the VSC whilst in the pit lane.
It's about the time you loose when pitting relative to the pace that the rest of the field are running. VSC or not, your time to pit will be fairly similar excluding entry and exit speed - your slowest points are under pit lane limits plus the time to complete the stop, and these parts are relatively constant and similar across most of the field. The larger difference is dictated by the relative pace of the rest of the cars at the time of your stop. You loose less time relative to full race pace because track speed is slower when under VSC. If you pit under VSC you loose less time (a net gain) against the competition, and you loose even less time by pitting under the real safety car because it is even slower.
The reason we have VSC is because the real safety car is so slow compared to the operating window of an F1 car on slicks, so much so that tyre temps quickly drop out of the operating window which ultimately causes more crashes when the race restarts - you suddenly have 19 cars (because one just crashed) bunched up behind the safety car with cold tyres ready to gun it the moment the safety car pulls in. So, VSC allows cars to keep tyres closer to their operating window by allowing a pace that the real safety car just can't achieve, therefore hopefully less crashes with yet more safety cars making a bad situation worse.
Yours, a former F1 consultant.