Mmmhh, to my surprise you're right. I didn't encounter any occasion yet with an implemented pure virtual function. So it't correct, sorry.
Thus I think the best would be to have a check box to decide whether to implement pure virtual functions, too.
Because it takes some doing in a bigger header to uncheck all the virtual functions. (You have to find them first beacuse they are not marked in the overview.) Or at least at a "= 0" in the list.