Saying
AF447 orange box did NOT record what was seen on BOTH screens
is very different from saying
What's recorded in the orange box may not include 100% of what's displayed on the pilots' screens when electrics or software anomalies creep in.
The RH displays on AF447 was never going to be recorded by the FDR regardless of the condition of systems or aircraft.
Yes, that's when everything works.
It is even so when not everything works.
The limitations of an FDR is the number of parameters chosen and their sampling rate. Both of which can probably be improved quicker and at less costs than installing one or more video cameras and associated equipment. Most QARs record more detailed data than the FDR already.
The desire to have cameras in the cockpit seems to me to be more about having the latest and shiniest tool even though it does pretty much the same as the old ones.