UEFA instructed the players to wear full kit . The reason Terry celebrated is because he has been at the club since he was 14. I'm betting Stevie G would've done the same.
I don't see why wearing shin pads would be a problem if he's got the full kit on? They do hold the socks up after all
He then got pushed to the back by the other players, even Lampard pushed him back after they jointly lifted the trophy