If the gravity is still high, why do you want to rack over? If it is not there yet, then that means it's not finished fermenting yet. So you don't want to get it off the yeast yet.
The secondary is for
clearing and you move it to that vessel AFTER fermentation is completed.
And even if it hits the grav mark quickly the yeast still have a lot of work left to do, they like to clean up the byproducts of fermentation, that can lead to off flavors....So rather than limit the number of yeast to do that job, leaving it a few days more, let's the optimum amount do their job.
Even Palmer talks about this in How To Brew;
Leaving an ale beer in the primary fermentor for a total of 2-3 weeks (instead of just the one week most kits recommend), will provide time for the conditioning reactions and improve the beer. This extra time will also let more sediment settle out before bottling, resulting in a clearer beer and easier pouring. And, three weeks in the primary fermentor is usually not enough time for off-flavors to occur.
That's why many of us leave our beers in primary for a month, OR wait 14 days before racking to a secondary anyway...Many of us don't even use secondary unless we are dry hopping or adding oak or fruit to the beer, instead we opt for 3-4 weeks in primary, then bottle.
that way we give our yeast plenty of time to do their thing....there is abosolutely no harm in waiting...in fact your beer will thank you for it....
We forget this simple fact...We are not making koolaid, or chocolate quick, just stirring in and having instant gratification...when you pitch yeast, you are dealing with living micro-organisms...and they have their own timetable, and their own agenda...and it usually is different from ours.
In Mr Wizard's colum in BYO this month he made an interesting analogy about brewing and baking....He said that egg timers are all well and good in the baking process but they only provide a "rule of thumb" as to when something is ready...recipes, oven types, heck even atmospheric conditions, STILL have more bearing on when a cake is ready than the time it says it will be done in the cook book. You STILL have to stick a toothpick in the center and pull it out to see if truly the cake is ready.....otherwise you may end up with a raw cake....
Not too different from our beers....We can have a rough idea when our beer is ready (or use something silly like the 1-2-3 rule (which doesn't factor in things like yeast lag time or even ambient temp during fermentation) and do things to our beer willy nilly....but unless we actually stick "our toothpick" (the hydrometer) in and let it tell us when the yeasties are finished...we too can "f" our beer up.