NOOOOOOO! The decockers on these guns are 100 times SAFER than doing that is. (I'm guessing you're referring to pulling the trigger and thumbing the hammer down... )
Sigs and HKs are almost set up the same way- the deal is this-
You press the decocker and the hammer is dropped onto this thing called a
safety intercept notch- this is what blocks the hammer from moving forward far enough to
hit the firing pin. The sig decock is slightly more elegant than the HKs is, because the Sig
decocker kinda unloads the spring gracefully, but they're more or less the same. The
firing pin safety is also in effect during this time, so even if the notch didn't catch and
it hit the pin, the gun would not go off.
However, all bets are OFF if you touch the trigger while decocking, as this disables the FP safety and probably causes issues with the decocker. (touching a trigger whenever you don't want the gun to fire is bad juju with most modern autos anyways)
Point in a safe direction, and then actuate the decocker. Done. No need
to make it more dramatic than it has to be.
-Mike