Are jobs bound by lore?

[Rongway]

Then the only thing that makes machinist a job and not a class is the fact that it holds a soul crystal and it's just a terminology thing.

It still doesn't change the fact that for certain disciplines a soul crystal is 100% required and for others no teachers exist. Even blue mage requires a job stone for blue magic to work despite the fact that it's also blank, like machinist's. Enemy abilities that you learn are stored in the soul crystal. That may be a piece of lore written by game mechanics, but it's still in the story of how things go and it's impossible to be a blue mage without one. Then there's the other jobs I also mentioned where it's also completely impossible to be one without holding the stone, regardless of any training.

You have some good points but I think what we've come to is a set of slightly different questions.

Norvrandt has a few jobs that are very much like Eorzea's White Mage, Black Mage, and Paladin, which they call Devout, Magus, and Knight, developed independently but with many overlapping techniques. Suppose, somehow, an Eorzean Black Mage happened to encounter a Norvrandtan Magus.

• Would the Black Mage recognize the Magus as a Black Mage?
• Would the Magus recognize the Black Mage as a Magus?
• If the Magus learned how to cast black magic without blowing themselves up not through a job stone but through a combination of talent and practice, and incidentally developed a set of techniques that matched the Black Mage's technique set 1:1, would it matter that the Magus didn't have a stone or that they styled themself Magus instead of Black Mage?
• Is only one of them a job because only one of them has a stone?
• Are they both jobs, but different jobs?
• Are they the same job?