it's not a drill or anything per se. It's more like a background physical proviso of the style. When your hand changes you more one finger at a time and you are also trying to extend all the way to the finger tips. Also we do a lot of hooking...you know like an upside down single whip and you are always twisting that to the max and holding that twist with the full extension eventually allows you to move everything as one thing through those tight little postures. It gives you really good grip strength since you're connecting the muscles of the fore arm and really the strength of the whole posture into your hand.
Anyhoo, it's always intersting to hear the minutia of other folks styles and try and figure out the intention behind them.
Best,
S