According to section 6.1 of the NCAA rule book, every ejection resulting from a flagrant foul is reviewed by the officials from the offending team's conference in order to determine of additional punishment is necessary. There was nothing out of the ordinary with the way his situation was handled. It wasn't an egregious call; they just reviewed it and found it borderline enough to not warrant additional suspension.
But seriously, if it wasn't a punch, what was it? How would you describe it? Whether or not it was flagged or should have been flagged, what do you think Koroma did or tried to do?