Is this a concern in order to understand reasons of PF persistent NU?
Yes, before switching to ADR3 the speed information displayed on the RH PFD will be 'unknown'. thereafter the information could be extracted from ISIS (share the same Pitot and static lines).
Was he following -wrong- FD orders, when this was available?
Mismatch between sides are recorded?
No, LH and (ISIS or Standby) are recorded.*
*Edit: BEA#3
Speed parameters
The calibrated airspeed recorded in the FDR is that displayed on the left-hand PFD, unless it is invalid
(if the speed is less than 30 kt, in which case the SPD flag replaces the speed
scale).
In this case, the airspeed recorded on the FDR is then that displayed on the righthand PFD.
BEA published information mentioned this?
Yes. PAR 4.3 of BEA Interim report #3
If existed a mismatch how we could learn what PF saw?
See previous post, I guess somebody can derive - possible FD orders-,
out of information from FDR traces.
If this specific point was covered earlier, please inform the link, if possible.
I don't know.