Gragnar the Mightily Tusked is a fighter. At first level, he took Orc Weapon Familiarity. This makes advanced orc weapons martial orc weapons for Gragnar.
I assume this means that, as his proficiency increases to expert, etc., in martial weapons, he also gains that proficiency with an Orc necksplitter.
But Orc Weapon Expertise states
Whenever you gain a class feature that grants you expert or greater proficiency in a given weapon or weapons, you also gain that proficiency in the falchion, the greataxe, and all orc weapons in which you are trained.
Does Gragnar have any use for this, if the Orc necksplitter is treated as a martial weapon and he therefore gets the proficiency increases?
If not, is this feat more directed at characters who don't necessarily get increased proficiency with all martial weapons? For example, an Orc Warpriest, who only gains expert proficiency with their deity's favoured weapon?