I'm thinking this is more of a demonstration that it can handle things like surges. Supposing that a sudden spike in your line caused a surge and your PSU ended up dumping something like 60V into it right before the PSU's capacitors themselves blew up. Worst case scenario, who knows what that voltage would be. But short of your house itself getting hit by lightning it's going to be under 1MV.
In electronics, too much current is basically the source of death. However, electric circuits have a fixed resistance. Too much voltage is then exactly the cause of too much current, unless you have a fuse. So, asking for 1MA or asking for a high current test is basically asking for an overvoltage test. Think about what happens when you overvolt your CPU. If it's the current that kills you and somehow these aren't related, then your CPU should run fine at 12V -- if you could cool it. But it doesn't, does it? Think about when we had 3.5" floppy drives and you plugged the connector on backwards. You reversed the 5 and 3.3V lines, right? And then that magical blue smoke came out and it no longer worked...