actually, hdwk108 is correct..
you guys are getting hung up on thinking that the downward strike is...a downward strike.
When doing the downward strike, You are developing downward energy.
This can be applied in a myriad of methods.
One example is a downward jut-sao, which with proper energy, can break the opponent's structure, or at least the trajectory of their arm-depending on their bridge sensitivity.
You need to stop looking at movement being simple technique, or rather, limited to simple technique.
Gung-Fu is a rich, vast method. If you limit your thinking, you limit your possibilities, and your understanding....or is it the other way around...?