I'll admit that I haven't tried this on other platforms, but I was under the impression that the opposite should happen: `/bin/sh` loads a basic POSIX-compliant shell that should work on other platforms, with Bash, Zsh, and whatever else, which are extensions of a POSIX-compliant shell.
sh will load whatever the OS decides it to open LOL; there is no rule. again why i just go with gnu bash as it is pretty feature rich and exec's other-cli-apps really well. the loops it can do, and arrays are just a bonus; if i need some more complex data structure, then there's another app for the job- that is not an interactive shell. just beware of the dragons when dealing with macos's old-ass bash; check out the version, go with new if you can
Blegh, now I have to do some digging...