Watch the video. They finally realized full flaps wasn't working for them,
and retracted the flaps back to flaps 40 about 15 seconds before they
finally hit the ground. They were definitely slow below their target
airspeed, but the stall was caused by them pulling up to avoid an
obstruction at the last second. Had they had the #3 engine in use I suspect
they'd have made it to the runway just fine, full flaps and raising them
back to flaps 40 and all. Your source was pretty accurate, but evidently
wrote what he did before the FDR data had been reviewed and it was found
that the #3 was left at idle by mistake. That's my opinion anyway, from
seeing the video and reading the summary of the accident report that the
USAF released.
Scott Wilson