The part I don't follow is how we arrive at the overspeed? Since altitude sensing (static ports open) appears to have operated throughout, then with the dynamic port (ONLY) blocked, indicated speed would fall (which appears consistent with what BEA is reporting).
Sorry, that is backwards. When you climb with a blocked pitot, the airspeed winds up, not down. Static is dropping and pitot pressure (trapped) stays constant. Delta P is higher which indicates higher airspeed. If I hadn't wound an airspeed completely around once climbing on top of an overcast, I'd probably be confused also.
