So... Why is it that a level 19 Gladiator can equip and cast Stoneskin (a level 34 Conjurer/White Mage spell), but a level 34 White Mage level synced to level 19, can't?

Just curious about the logic here, haha.

I was in a Duty Finder instance with a Gladiator and I was on White Mage. We were both level synced to level 19. He was casting Stoneskin on the party, and I couldn't even though it is a spell my job natively learns. Just didn't make sense to me.