Stark tells Rhodes that they are only coded to him when Rhodey asks for an armor in the beginning of the final battle. That's why he runs around without any until he gets his hand on the Iron Patriot armor again. And it's Jarvis that's controlling the empty armors. Stark just tried to levitate a bit inside his garage, which isn't really much relevant experience when it comes to flying at great speeds with great accuracy which he does with the first real test. And Stane had never been in the Iron Monger suit before the final battle because it didn't have a power source until then. Pepper doesn't stray from that line since she's a super being at that point of the movie. You don't have to like it but it's not a plot hole.