We're permitted to commence an approach regardless of the RVR. However, if any of the required RVR are below minima that approach must be discontinued no later than 1000' above threshold. If it's ok at 1000' you can continue and even if it subsequently goes below you may continue to DH.
Listening to the CVR it sounds like a request for flap 0 moments before impact... could be wrong but sobering nonetheless.