If you riding on a road and getting passed by a car less than every two or three minutes, riding single file is a no brainer.
My take on riding abreast comes from motorcyle riding where it’s also dangerous (and illegal). The safety issue is that in the case that you need to swerve to avoid something, you either get to chose to crash into the person next to you or (depending on which of the two riders you are) you swerve onto the shoulder/into the ditch or into oncoming traffic… neither prospect is much fun.
Ultimately to me it’s more about safety than annoying people driving cars… though I’m all for good PR for cyclists.
The scientific approach… I like it! 