I like how you did your tutorial, it is informative and I like seeing a range of sizes.
With that said, yeah, it is true some have to wrap an arm around their chest; I often have to, and that's only on the rare occasion that I run (and sports bras never help one little bit.)
I would like to point out that the measuring method you point out does not work very well for the larger sizes. When I do it, it often says that I'm 2-3 cups smaller than I actually will fit into.
As for back strain, it also makes some women slouch to try and hide them, or just from the weight, leading to bad posture if not careful.