Originally Posted by aerobat77
in my opinion this is not and simply cannot be the reason...
Completely agree. However there is one more mental trap that could hav been the case:
If they were taking off with Flaps 15 due to the relatively light load, but the mental picture of the PF was Flaps 28 (the more common setting), retracting flaps one stop would have an entirely different outcome due to the huge speed gap between 15 and 0.