CM,
Sorry. My understanding is that certification of a HUD as a PFR, to the demanded SIL, is very rare. HD Insts are more easily PFR compliant as far as standards are concerned for flight critical functions, therefore most FJ have a note in their RtS stating such.
The fact that aircrew spend 99% of their sortie time using the HUD (i.e "primarily" using it) is another matter.