That's true about the foragers. Forrest just took it as a given. Whenever his men encountered blacks, they scooped them up and sent them off, their situations to be determined by somebody else. I do give Forrest a few bent points for not profiting from it or letting his men do so. Longstreet knew Jones and some other partisans were rounding up anybody for sale but he happened to be polishing his boot top when they passed by with them. John Hunt Morgan was known to sell slaves to get a little extra money for his operations.
I'm a little iffy about no free blacks being sold, too. Forrest, for instance, had a fellow who claimed he was free but the guy he was working for had run off with their luggage, which included his papers. Forrest could have inquired but he didn't - off the man went! (Before the war he wasn't above being a little lax about paperwork - the marshal once busted him for selling six slaves who weren't slaves!)