Funny though that top of the range Premier/LS and also the Statesmans got the same guards (minus strip holes)....

HX and HZ didn't lose the GTS guards for any reason other than they were in the road of the SANDMAN logo. As I said the HX and HZ were the same as GTS forward of the firewall plus mirrors, bar the GTS badges and guards. This is the reson HX Sandman has the dual headlight front - it is what the GTS got. Same for HZ, Sandman just used GTS nose.
HJ was full GTS treatment on the front except for badges, HQ wan't. It used the HQ SS front, basically GTS guards and headlight surrounds with SS grille.