If I remember rightly, those "statistical analyses" comparing 4-engine to 2-engine aircraft were done as a joke, where the trick was to spot the statistical howler.
Well, the analysis I'm referring to was submitted to the FAA as part of Boeing's justification for 120 minute EROPS (as it was then known).
The FAA must have missed the joke
Oh, and at that time, the requirement for 120 minutes was a shutdown rate of o.o6/1000 hrs., and some engine types were struggling to meet that.
Today most engines are well below o.o1/1000 hrs.