quick, it's not totally wrong, and your experience doesn't disprove the claim, does it? It just shows you did well at your MA.
I actually think not enough students at very good universities get firsts, or high firsts.
holly - yes! It feels so cruel and depressing to be constantly saying 'yes, this would be an excellent A Level answer, but ...'.
One of the eternal issues is that students seem to be taught a particular structure of essay, where the introduction and conclusion are mirror images, and a particular style of argument that relies heavily on claiming things are 'relevant' or 'important' and making huge, exciting-sounding generalisations.
So, sometimes, success at A Level can be actively damaging in the early bit of a degree, especially if the student isn't adaptable. Same with undergrad and postgrad.