It seems you are not understanding what the point is here.
SailJail is not about locking apps out from files you place on the phone - it’s about locking out apps from system files, dotfiles, config files, other apps’ files and so on and so forth. Things they have no business having access to. Just place your media where it is supposed to be located, and all will work fine.
SCP.
You not knowing this makes it even more certain you don’t know your way around a Linux system - which is fine, but then moderate your criticism accordingly.