He shot Goyle his best Hermione-inspired withering look. "Of course I bloody know who you are."
Ron was left with two possible conclusions. Either George had gone full-on mad inventor with his new product ideas and become absent-minded to boot, or he hadn't told Goyle because he thought it would be funny to see how they both dealt with the situation; Ron didn't know which way he was leaning.
"He didn't tell you that I'm his new partner." Technically true, though in a minor way. Ron had invested in the business after taking advice from both Bill and George, proving that having talented brothers wasn't always a bad thing. "I work here now."