It definitely kicks the power light on for a bit under a second on my 2010 era desktop. The (high end, low wattage) power supply is delivering enough voltage to keep the motherboard power controller up.
I have no idea if it discharges all the different voltage rails. I don't like having the fans try to spin up while I'm mucking about, and it stops that from happening.
Of course, from an equipment damage perspective, grounding yourself to the case ground is much more important than discharing the PSU capacitors.
I usually physically unplug the computer, push the power button, then open / touch the case (I'm in a humid climate).
I've never had an issue (ignorging fires, but those happened when the computers were intentionally energized).
I have no idea if it discharges all the different voltage rails. I don't like having the fans try to spin up while I'm mucking about, and it stops that from happening.
Of course, from an equipment damage perspective, grounding yourself to the case ground is much more important than discharing the PSU capacitors.
I usually physically unplug the computer, push the power button, then open / touch the case (I'm in a humid climate).
I've never had an issue (ignorging fires, but those happened when the computers were intentionally energized).