Isn't that a possessive form? As in: Waiter: "Can I get you guys's orders?" Non-standard (as written: "you guys' "), but speakers notoriously add extraneous "

Isn't that a possessive form? As in: Waiter: "Can I get you guys's orders?" Non-standard (as written: "you guys' "), but speakers notoriously add extraneous " 's"s. (Sidenote: when we were teenagers my sister and I referred to one pastor as "the polytheist", because he always said "in Jesus's name", which we chose to interpret as "in Jesuses' name". God, I'm a nerd.)