User blog comment:Metadwarfosis/In anticipation of volume 11- Dwarven Kingdom and Expectations/@comment-41.227.106.20-20160709190512/@comment-27008999-20160709224505

It's not about being a guild master, but being able to use items that Nfirea can use. So technically, even if Nfirea carries the guild weapon he won't be recognized by everyone else, just the system of Nazarick and the staff itself accepts him.