To Wanda's knowledge, there also wasn't a whole secret prison under her own feet, so anything was possible. Tony shouldn't have expected that the Brotherhood would be so easy to keep tabs on, though. Magneto was a wily bastard, he had to give him that. Don't even trust your own blood with your secrets and you're bound to be unpredictable.
"I believe that is all I require of you at this time," Iron Man announced, fists at his sides again, any lingering awkwardness put aside to manage a respectable departure. He didn't need Wanda's last image of him a negative one, that could undo a good long distance relationship.