That description must be airbus
On the 737 the FPV does not replace the FD and both can be used indepently of each other. And the FPV is of course switched on and off on the EFIS control panel. Anyway, no caged FPV on the PFD available, only on a HUD.
PFD Indications change a bit with activated FPV though, a track indication appears on the horizon line and selected course will be displayed as a small mark on the horizon line.