Mage-Ring Responder broken by Act of Treason

Whenever I steal an opponent's Mage-Ring Responder with an Act of Treason, it no longer requires a match-five in order to attack. I usually thought that the X disappearing was a graphical glitch since I would almost always immediately sacrifice it to Fiery Conclusion, but in the Story game I just played, not only was it able to attack after I stole it, but when the AI got it back, it STILL didn't require a match-five in order to attack me back.