He says, that this is ok at my (in his opinion rather slow) high speed, but if he's up at real high speed (over 65mph), he stays well in the hind seat. His argument was that you've less base contact and thus less risk that an edge could contact slightly uneven snow.
I think he is wrong. It's just that high speeds have a very big stabilizing effect. As has been mentioned before, if the weight is back, the board will want to pivot if there is a disturbance.
I've only ever caught an edge at relatively low speeds (knock on wood).