Wrong, it's aesthetically correct that some Gundabad orcs had dwarfs heads & skulls as trophies, bc long time ago Gundabad was the first dwarven kingdom where Durin, father & the firstborn from all dwarven clans, woke up with his partner, so, for the dwarves Gundabad it's no just other settlement, it's the most sacred place for them & the easiest way to provoke the Dwarves. Also, there are specifically Gundabad warbands what are professional headhunters, a kind of orcish bounty hunter.
I don't know if Taurion planned some kind of effect for the headtaker units, if not, maybe those orcs could be unbreakable and/or cause fear to dwarves by the trophies.
PS: Btw, happy new year to all.