Mandating HUD use is perhaps a poor SOP.
Touchdowns might be more accurate in the primary mode with FD guidance. In this accident the offset LOC prevented accurate computation of precision guidance and the HUD mode was changed (Page 28).
FPV was still available, but the Captain considered this to be too much information. FPV is a valuable tool, but if not well practiced it can be demanding. Furthermore the vector has to be referenced to both a desired approach slope (probably the same as the GS in this case) and a ground reference point – the intended point of touchdown, e.g. PAPI. There are no indications that this was the situation nor that it would be easy for this approach, thus the HUD could have been a considerable distraction.