Inability to enchant level 5 Enchants - Busted!

Ok, so a normal day grinding out in the wild.
As usual when I hit level 30, I go to enchant a sword.
So the title says it all, now here's the picture -

And yeah people, the enchant is a Knockback 2 and Bane of Arthropods 5 diamond sword!!
And based on what others tell me and I know, you can't enchant a level 5 enchant anymore.
But why is this so? Why is it possible I got a level 5 enchant on a sword?

Not possibuurrr!

IKR! Thats what I thought too!

Arthropods is still possible, only some others are not possible, look it up in the Wiki, I read it there.

Oh, but is this in any sort of case, rare?

Yes.

Also ill buy all of your emerald ore at 1783....

V aint gone, just became uber rare, I got Eff 5 on my shovel after 1.3

I think the Wiki is incorrect - it's ether VERY rare or not possible but only on diamond picks.

On Swords you also can get Site V

I don't think V is possible on diamond picks, I've only gotten V on iron picks so far. But I've got smite5 and Bane5 few times on diamond tho

My bad, by that I meant V is only possible on tools other than diamond picks I think.

Could be possible, I've enchanted alot of picks but havent seen V after 1.3 on diamond picks yet. I've seen V on diamond swords, and iron tools tho.

Yeah

on Gold items they have a high enchantability.. so.. you'll get V's alot more often than any other material.
Diamond is like.. 3rd or 4th ( out of like 4 in weapons and out of 5 in armour)