Thanks for the explanations, especially the snowless photograph!
Bizarrely, just yesterday I spent an hour explaining to someone about the Aeroperú 603 crash and how a partial blockage is harder to spot than a complete one. But I thought that in that case, the readings are too low while climbing and too high while descending which doesn't seem to map with MVP3.
Regarding automated heating: that it isn't at all clear that the pilots didn't turn the heat on (or that it wasn't automated), just that they didn't manage to diagnose the issue in the first minutes of the flight.