Thank you, Takata for the diagrams and pages of info.
The info as presented tries to pack too much into a page, mixing pitot and static pressures together.
AFAIK, all the prior events were airspeed errors alone, and did not have altitude errors. Airspeed and altitude are separate and unique functions within the ADR, except at low speeds, and their output data bus words are separate and unique. An ADR may flag or put out erroneous airspeed without affecting altitude output.
The FCOM Bulletin #009 page 3 gives the case for total pitot obstruction, not just drain hole obstruction, although it is known that Thales pitot were prone to drain hole obstruction due to roughness in the holes. Drain hole obstruction without impact air obstruction will give an erroneous higher than correct airspeed.
Total pitot obstruction, per page 3, puts the plane into an unstable situation. Increase of altitude cause increase of IAS. The A/P will try to increase pitch to reduce the IAS, causing even higher erroneous IAS. This is in accordance with Der Spiegel story.