xargs is not a counter example. It is not a shell builtin, it is a program that takes a bunch of string arguments like every other program a shell would call.

xargs is not a counter example. It is not a shell builtin, it is a program that takes a bunch of string arguments like every other program a shell would call. xargs -0 -n1 bash -c 'mv $1 ${1//.js/.ts}' -- Everything to the right of xargs is a string argument passed to xargs.