I have to confess I was in a mixture of bemusement and amusement when I read that the "main goal in checking the flight controls is to make sure you're (sic) seating position is correct...".
Now, forgive me, but I'd always thought the main reason in checking the flight controls was to verify the correct operation of said flight controls!
I just want to add up to what others have correctly pointed out about the goal of the flight controls check. First, not only your seating position should have been more or less dialed in during TR training, but the SOP section, specifically PRO-NOR-SOP-07 "
Before Pushback Or Start", also states to check your seating position, along with "seats, seatbelts, shoulder harnesses, pedals and armrests". So there you go, that's the proper time to do so. Not at flight controls check. And yes, I do set my seat and armrest at that particular time, though minor adjustments may be necessary depending (usually) on the age of the particular airplane and/or how hard previous colleagues have treated their machinery, which in any case, isn't a major distraction from flying duties.
Regarding the PM being too "heads-down" during the check: it takes about 20 to 30 seconds for both flight crew members to check the controls. The FCTM points out that the check should be done
"at a convenient stage, before or during the taxi", and I'm yet to read an accident/incident report, or a recommendation of any kind, via Airbus or any of the operators I've flown for, where this is identified as a less than adequate way to perform this check. Just be sure to do so in a time and place that you know you will not get a particularly high workload for the aforementioned 20-30 secs and you should be fine. If you do run into high workload, you can always interrupt said check, take care of whatever has arisen and repeat your check from scratch once you're done. You know, basic airmanship concepts.
P.S.: I'd have the time of my life messing with the fellow aviator next to me to try and get them out of "automatic mode" having the "freedom" to do the flight control check in whatever axis I choose. Nice gotcha and giggles to be had there.