Cross class skills: why does CNJ have botany and mining skills available?

[Niwashi]

The base classes are a relic of the 1.0 system, and allow players to access all cross-class skills from all classes.

Not quite all. The crafting cross-class skills, for instance, are only crossable to other DoH classes, as there would be literally no way for a class that doesn't craft to use them.

And while some DoL skills (the ones pertaining to finding gathering nodes) are crossable to DoW/DoM classes, the level 20 ones (Byregot's / Nald'thal's / Thalik's / Nophica's / Menphina's / Llymlaen's Ward) are cross-class-able only to other DoL classes, because those ones can only be used while gathering. (I believe in that case, the actual rule is that they're assignable by any DoL class, but really it's only useful to cross the BTN ones to MIN and the MIN ones to BTN. FSH has no use for any of them, but I believe is still allowed to assign them to cross-class slots anyway.)