If you have your key handy that certainly works, too, but in practice I almost never have my key out. It's only a minor hassle to dig it out my purse – but I was happy to find a way to optimize.
Interesting. It may be version dependent, or the behavior may depend on the car being "asleep" to some extent (though obviously not the deeper sleep that has been removed in 4.2 since I still use the technique on 1.19.42.) In the morning I find that if I press lightly for a moment on the latch the brake lights flash as it unlocks – and I'm good to go.