It is also written in the Airbus FCOM that you have to adjust your seat just before performing the "Before start checklist" and requesting the start clearance.
Does this mean that I am not allowed to adjust the seat for the rest of the flight?
And what happens if I adjust my seat before the FCOM tells me to adjust it?
What happened to common sense? Whoever told you that you have to keep your loudspeaker at the 1 o'clock position when you wear the headset is clearly lacking it.