Sorry TJ but it doesn't. The FAC status of anyone who might be accompanying the FAC holder is irrelevant in this case - it might of course be very important if there was one of those horrible 'mentoring' conditions though.
If the condition contains the wording "..........land deemed suitable by the Chief Officer of Police for the area where the land is situated and over which the holder has lawful authority to shoot", or something similar, then it means exactly that. Doesn't matter if the accompanying stalker has an open FAC, is a professional, or whatever. If the land isn't cleared for the calibre on the restricted territorial condition then he won't comply.
BTW. Once a FAC is opened up Devon & Cornwall will usually just insert a single simple condition covering all the firearms and ammo on the ticket for any number of different quarry species. It's then up to the holder to decide which firearm is suitable or legal for what he is intending to pull the trigger on. Makes life a bit easier being treated like an adult.