I would dare to say that the proof is in the kilt and not the school or guild.

If we were to take this line of reasoning to the extreme (as it seems they are) only descendent's of certain blood lines that still reside in a certain area of the world would be deemed to have achieved "master" status.

Seems to me that by saying "There are only two Master Kilt-makers left" is a way of self aggrandizement to the extreme.

To be a Master is to teach the way; it is not something to be clutched tight to the bosom and never shared but rather shared willingly with those who seek the knowledge, and willing to walk the path.