In a fully functional EIS (which is PFD, ND and MCDU, not MFD) it is not possible that you can have FPV and FD displayed at the same time.
The ACARS message FLAG PFD is there as a proof that bird had been selected. But it does not say for how long. My guess is that they selected it, saw the flag, switched it off again. The time of the selection would be too short to show on the graph.