Interesting. I’ve never tried it out, but I assumed that an RCD / GFCI would trip more or less instantaneously. I’m kind of surprised you felt much of anything.
Luckily, electricity is about 20x safer as long as it is supplied for less time than one heartbeat[1] - ie. 500 milliseconds.
Thats how RCD's can be so lifesaving even though they are relatively slow.
[1]: https://en.wikipedia.org/wiki/Electrical_injury#/media/File:...
Imagine you had an ideal switch that could disconnect a circuit instantly.
Any devices powered on that circuit with transformers, inductors or motors in (think vacuum cleaners, power tools, microwaves, blenders, etc) will have a current flowing through them, and as that current is interrupted there will be a huge voltage spike - easily 10x the normal voltage for a few milliseconds.
If a human is touching that circuit, the 10x higher voltage will cause 10x more current to flow into the human.
Hooray - your 'safer' RCD kills more people.
The real solution is to have a more complex switch which disconnects the circuit at the same time as shorting out the circuit, to allow any current that was flowing to gradually dissipate into the wiring resistance. To my knowledge, such things don't exist today.
Luckily, the problem I described is almost a non-issue. Deaths due to electrocution in buildings with a GFCI have fallen to pretty much zero - there were only four deaths due to electrocution at home in the UK last year (where voltage is very high and RCD's are common). That figure includes deaths by suicide, lightning indoors, and deaths where an RCD wouldn't help such as poking around inside CRT's, so it's entirely possible an RCD is already saving every life.
Now divide 1000ms to 50Hz.
@londons_explore pretty summed it up and gave a link to a very good graph.