Good Lord son, "the rejects of those were spun into 11/32"'s." Not hardly.
Tighter grained wood in 11/32 can spine as high as 100# or more. The 23/64 can spine as low as 45 to 50 pound. It is the density of the grain that makes spine, in conjunction with the diameter. Density also adds weight, so you can actually get heavier 11/32 than 23/64. I think folks at one point just liked the wider shaftting and probably supposed it was sturdier because of the broader cross section. I doubt it is, but some folks think so.
Decades ago, you could rarely find 23/64 unless you special ordered them. I like the smaller diameter myself. You can also buy 5/16.....which are NOT spun out of rejects either 8^).