Izlude always has Level 8 Jump because his is NOT using the Lancer skillset. He's using a special Jump skillset containing ONLY the two level 8 skills. Also, Jump skills are set to 50%, and with no other skills to learn... anyways, I've noticed that secondary skillsets don't work the same. Secondary skills, such as Izlude's Jump are set in the Battle Events, so they might automatically have all those skills. Wiegraf has a Punch Art skill, and it isn't the full Monk skillset, either, so I think this is true.
I've heard that when learning skills, the AI starts from the top. So for say, Wizard the skill list goes:
It will try to learn Fire first at 90%, Fire 2 at 65%, Fire 3 at 40% and Fire 4 at 30%.
In other words, while it COULD learn Fire 4 in chapter one, it's really unlikely. First it would have to have enough JP, which is 850... which is Job Level 5. Second, it would have to not spend that JP on another skill, which means it would have to fail the 90% chance to learn Fire, and fail to learn Fire 2 and 3 first. I've seen a Wizard with say, Fire 2 but not Fire before, but going down the list it because increasingly unlikely this sort of thing will happen.