Actually, it's other way around - amps matter a great deal.
400 volts with low amps feels like a sting. I've touched 25K volt contact once (by mistake), while unpleasant (and some damaged skin), managed just fine - cause very low amps.
I think what you're after is that the impedance matters a great deal - a high voltage but high impedance source will drop in voltage a lot and not deliver a large current into the body.
In both examples I gave, the PSU DC bus and the car, both are much lower impedance than the human body and the difference is likely negligible.
