It was a joke, you are, of course, technically correct, there’s no requirement for the mean and median to be the same.
That said,
If the mean and median were the same your statement would still not be always true. For more than one reason.
I’m interested, in what cases would it not be true if we assume “average” here to be “median”? I can only think of one: if we consider “understanding” to be discrete rather than continuous.