For the sake of arguing on the Internet, I have to disagree with this. Those are landmasses, physical entity that is only partially linked to to the human geographical construct of a continent. If the concept has any meaning at all, then there are at least 5, with Africa being one of them.
1) why would we count artificial waterways that require active maintenance to not simply close up again and
2) the Panama canal doesnt meaningfully link the two bodies of water. Its a series of locks and pump systems that allow ships to travel through an artificial freshwater lake above sea level.
