Zeffy, so without precision centreline guidance (offset LOC), the HUD could only be used in the ‘visual’ mode, and except for the flight path vector, the landing has to be made on what the pilot can see ‘outside of the HUD’. Also AFAIR, the ‘self generated GS’ is actually an aircraft referenced descent angle for FPV comparison – the GS is not earth referenced as the ILS GS is.
So if the approach and landing involves poor visibility or weak runway lighting, then the HUD is of no great benefit and if it detracts visual attention from the real world, it could be a hazard.
The link is mostly sales blurb, but in the VMC mode I assume that the FPV is based on an inertial reference opposed to being airmass derived. If the latter, then there might be some very interesting flare results in a tailwind.