Tony’s a little weirded out by Thor. Not because of anything personal, but because he’s from some other reality and clearly knows a version of Tony and Tony’s been having an existential crisis over the whole thing alternate reality/clone business. There’s a part of him that suspects that Thor’s going to be disappointed in him for not measuring up to whatever the Tony Stark of his world is like. So he feels extra pressure not to be a screw-up and measure up to this imaginary standard of whatever Thor’s used to dealing with because he wants him to like him.