Does Bob Mayer not owe that truism to Malcolm Gladwell ?
At any rate, I’ve read and heard Gladwell on the subject, but not Mayer. Gladwell does a good job of explaining the idea, and only somewhat overstates it, IIRC.
It sounds (from your summary) like Mayer may over-emphasize the significance of the number seven, for dramatic effect. I’m not familiar with Mayer, but I’m imagining he’s used to a fictional lens on cause and effect.
I’d say there’s a more intelligent/accurate and less dramatic/misleading explanation for what both of them are talking about, and that NO, there is no one magic number SEVEN involved. But there is a core truth that unusual accidents tend to need to involve multiple mistakes, because people naturally try to avoid disasters, and we tend to notice things we don’t expect to happen, and yes multiple things going wrong at once does therefore tend to be what precipitates major disasters. BECAUSE THAT MAKES SENSE IF YOU UNDERSTAND CAUSE AND EFFECT, and NOT BECAUSE SEVEN IS A MAGIC NUMBER.
Of course, a writer wanting to get readers’ attentions, may be unable to resist the temptation to frame evidence in terms of finding (or creating a story about) a pattern of seven being a magic number, but reality is much more complex, involving vast numbers of circumstances, and analysts or fiction writers need to condense that down to something comprehensible to make sense of situations.