Don't count on that all glob parameters on the command line will have been expanded by the calling shell for you,

I seriously doubt that the quoted warning means that. I think the warning means you ought to use opendir/readdir/closedir instead of calling glob.

Expansion of parameters by the shell (and Unix shells do more expansion that just '*') is the responsibility of the caller - (s)he decides whether or not to call something via the shell or not.