Well I know that we have been through all this before (in about 50 pages in the other thread)
but just to stick to this latest topic, The FAA has every right to question the pilots decision according to the regs, however this certainly not proma facia evidence of a bad decision by the pilot.
There is some allowance for allowing the pilot to make decisions like this due to only a minor degrade (subjective as it is based on the previous threads pages of posts) to overall flight risk.
Such overall risk includes consideration of Air-turn-backs, contaminated runways, air traffic, fuel dumps, overweight landings, diversions to unfamiliar (to the crew) airports etc.
In the long run, the FAA questions will likely go beyond this one incident, although it does give them a key to the CAA door. It will likely revolve arround not just this one flight (which was minisule in increased risk) but to the greater fleet risk increase if every crew would perform the same action as an SOP without the threat of being questioned about their specific judgement by a regulator.