Current limit into a short with a RCD will trip it in under 2 cycles, same as an imbalance. The caveat though is the RCD can take 5 cycles after that to start to open, and if it is a short then arcing will occur across the contact gap until the arc breaker bars finally cool it enough to stop. This can take 15-20 cycles of the mains until the contacts are far enough apart to stop arcing. So if you are a ground path and the current drawn by the DUT is 10A or so the device can take a half second to disconnect, even though with a 30mA test current it will be open circuit in under 5 cycles. Being shocked for the half second will definitely hurt you, and if the current path through you is to low impedance ( wet skin on both contact areas) there is a high current that will flow, in the order of a half amp or so worst case. Definitely enough to stop the heart in many cases, so YMMV here.
Kind of like stepping off the pavement into traffic without looking and walking across the road. You might get across a good number of times but eventually you will be a road pizza. Test the RCD with a 10k 1W resistor between line and ground, not your finger. Otherwise use the test button, which does exactly the same internally, using a resistor connected so as to create the imbalance current across the main sensor coil.