Looked to me like he was taking evasive action to avoid contact. Of course he may have exaggerated it a bit to win the penalty but that is not the same as diving. A leg was dangled out and he won a penalty. If this was Spain the locals would be celebrating his skill.
Good to see Maddison getting back to his best form. We have missed it. Alongside tielemans barnes Daka etc we have quite a potent and entertaining attack.