WPs for Host Armor melee

[Ecanoya]

Sorry if this has been asked before, but I can't seem to find any answers on this: what weapon proficiencies do melee weapons grown onto host armors use?

Specifically if I have a forearm bone blade, could I add the bonuses from WP swords and fencing to it? And if I had one on each arm, could I use them with WP paired weapons?

I feel like this is a case by case basis depending on the weapon, but figured I'd ask in case there's an official ruling I keep missing or something.

Thanks in advance.