> Though in general I find argparse's default behavior more useful.

I’m not sure I understand.  Why is it useful for an option parsing library to heuristically decide, by default, that I didn’t actually want to pass in the valid option that I passed in?  Shouldn’t that be up to the caller (or up to the program, if it explicitly decides to reject such arguments)?

Keep in mind that the caller might be another script instead of a user.