RE: My first exposure to SOS was for "save our ship;" "souls" was a pious emendation later on.

Me too, but i have since learned, when a plane goes down (and maybe a ship too) the passengers are refered to as souls, maybe not always in the newpaper, but by the investigators, and authorities, (FAA, Crash investigation team, etc).

it seems to me, a commercial ship sink with "Hands" (small fishing boat capsizes, 3 aboard, all hand lost..) and a passenger vessel has souls..
(with hands, both officers and seamen are equal in death, with souls, crew and passengers are equal.)