I think the major mistake in your statement is that the billionaires would lose more than a few million. But yes, they have reversed trades when people take advantage of flaws in automated market-marking scripts.
When were trades reversed when a market maker had a bad algo? If you are doing market manipulation, sure, your trades might get reversed, but if someone wants to puke money across the tape it's absolutely legal to take it.
I'm not able to find the story now, but there was a European (UK?) youngish person (teen?) who took advantage of bad market maker code to make hundreds of thousands. Those trades were reversed. The trades were under US jurisdiction.
