I am sorry, you’re totally right, is it pretty unreasonably nit picky to differentiate between 10 inch screens and 3 inch screens when it comes to web UX. Smart phones do count as all mobile devices and the only thing that matters when determining if a site is mobile friendly. And of course it’s usually a good idea to broaden the argument categorically to something larger than your personal experience to make the stronger point that most people would agree with you and the other person is obviously up in the night.