Are jobs bound by lore?

[MikkoAkure]

Though this raises a question: If an Astrologian requires a soul crystal for their spells, how is Urianger one in Norvrant?

Didn't think of that. Probably an oversight. Or maybe because his body itself is present with the soul stone? Anyone's guess at this point, but the game system describes him as a full-on Astrologian and it's a pretty important plot point in the AST quests that Levava's grandfather needed that stone in order to cast AST spells.

The same way Jannequinard does I assume. Also Leveva post level 60 has let anyone who wants to learn Sharlyean Astrology to do so. Which is similar to Geomancy and last I checked the Hingan we meet in the SB questline doesn't have a stone. That and anyone who won a riddle contest that lasted for seven days against pixies probably can find a way to switch from a 1.0 arcanist to Astrologian.

Levava's grandfather is presumably a better astrologian than Jannequinard and he required a soul crystal, becoming powerless after giving his to us. It could be that smaller scale spells don't require anything special other than training. Just like how conjurers can pull aether from nature and also cure people on their own with just a little help from the elementals and a teacher. But we never see any of the conjurers casting assize or holy.

Regarding Geomancy, I think it has a lot more in common with conjury than astromancy. Both source their aether from the area and elements around them.