My more or less educated guesses:
- Providing O2 support at the correct altitude need probably not mean that the oxygen pressure within the lungs remains equivalent to MSL, so maybe at 40,000 ft it is lower than at MSL (although still sufficient)?
- Apparently, suction AIs do indicate a climb when the airplane accelerates: "Acceleration and deceleration also induce precession errors, depending upon the amount and extent of the force applied. During acceleration the horizon bar moves down, indicating a climb." (Source:
attitude indicator (artificial horizon))
- Experienced pilots perform their tasks almost automatically, without having to carefully think about what to do (next). This makes them quicker and more efficient in their actions and with more spare mental resources compared to someone inexperienced, but also increases the risk that their "automatic" responses are wrong, for instance when the environment has slightly changed. Some examples can be found, e.g., in
Skill-, Rule-, and Knowledge ? Based Behaviours and Associated Errors . It also increases the risk for lack of concentration blunders since the mind prefers to wander around rather than focus on a task that has become routine and dull. In the words of James Reason: "Paradoxically, absent-mindedness is the penalty we pay for being skilled; that is, for being able to run off our routine actions in a largely automatic fashion" (Reason, J., 2008, "The Human Contribution", Farnham: Ashgate, p. 44).