No it isn't.
Antiquated gear is job locked too.
I know, because it's a major pain in the butt to Glam my Squadron because everything is job locked. (Well, not everything, but a lot of stuff, especially dungeon/tome gear)
Then, pray tell...
What happens when you get a weapon for a different job to your own and then right click it, then select "Equip"? (Such as when you first unlock a class)
Does the game explode? Does reality cease to exist?
Or... Do you simply equip the weapon and simultaneously remove all other equipped gear?
Since, I know for a fact it is the latter.
If the unlikely event that you're wearing ARC specific class gear while having a completely full Armory Chest and Inventory...
Then... They could simply make the game auto-equip your Summoner job stone when you log in (Just like how if you make a gearset with a weapon, then remove the weapon from your Armory Chest and try to select that gear set, the game will auto-select another weapon for that job from your Armory Chest)
Since, you'd have that. Given that pre-level 30 all gear is generic DoM stuff. Thus in order to have ARC/SMN specific gear, you'd need to be over level 30 and thus likely have SMN job unlocked.
If the case is, that you're one of those level 70 Class people whom hasn't done the job quest to unlock SMN and still has a full armoury chest and inventory... Then IDK, maybe SE gives out a free SMN stone to every level 30+ ARC and does something with the job quest to bypass the need to be given a crystal from the initial quest.
I mean, we literally could have stopped debating when this entire thing was noted to be unnecessary work for the Devs.
You know who doesn't like having a bunch of unnecessary work to do?
The Devs.