Barrage can't be socketed into cast on X

Despite Barrage being a spell it can't be put into cast on shock or any of the cast on X spirit gems.
My first guess is due to it being a buff spell, which seems to track as charged staff also can't be socketed despite also being a spell.

I'm guessing anything that is self targeting is not being tagged correctly in the backend as spells, but rather tagged as Buffs. The incongruency is rather annoying.

Cast on X probably needs to read "Cannot cast Buff Spells". And then skill gems that are buffs need an added "Buff Spell" to the tag line rather then just "Spell" as well it isn't be treated as if it is just a spell.

Have we ever gotten an official statement on this if it's a bug or intended ? Barrage has the tag Spell and thus should be able to be assigned to Cast on X which trigger Spells. Both Curses and Mark works for example, but Mana Tempest and Charged Staf don't (both Spellswith tag Buff). As stated above the issues seems to be with the tag Buff.

Any Update on this?

I am also interested in an update. As everything reads it should be socketable, since Barrage is a Spell.