That's perhaps the slightly wrong way of looking at it. "rm" is an executable that parses its command line; the asterisk is a special symbol that gets expanded

That's perhaps the slightly wrong way of looking at it. "rm" is an executable that parses its command line; the asterisk is a special symbol that gets expanded to a list of all file names (except those starting with a period). So the arguments `rm` receives when you type `rm *`, is a list of all file names. It does not know that, because all arguments are just strings, and therefore it parses those strings the same way as if they had been typed, which makes that a filename like `-rf` can trigger the behavior of the "flag" `-rf`.