Fellaini should have been gone regardless, but that kind of 'embellishment' puts the official in a terrible position. Because it isn't truly a dive, nor simulation. Just silly exaggeration.
Not to mention I believe simulation can only be called during the run of play - so if you book him there, it has to be for 'misconduct' which has its own set of standards.
edit: I'm going to correct myself. He can be booked for unsporting behavior there - 'shows a lack of respect for the game'. Works for me. The line that allows for a caution for simulation deliberately uses the word 'foul' and what Fellaini did was not a foul.