Keeping a post on track can be “...properly torqued at assembly...” is an attempt to eliminate the noise from the good data. It’s as close to normalized as we can get without actual experimentation. Finally, I will tell you that in a bike shop environment, the left side crank, (square taper or diamond taper) is the one most often found loose. Call that anecdotal if you want, but it is my real world observation. Second is data based: do a search on ebay of quality used cranks and you will find more right hand cranks in sale condition than left side cranks. If there are fewer left side cranks for sale, something has happened to them. I’m guessing damaged taper walls.
In the end, thanks to the truly curious and thoughtful folks here, I’ve digested the valid information and that helps me understand the problem better.