Voll's Protector Ironclad Vestments only generates 1 power charge per cast of Bonestorm

So, Bonestorm scales it's AoE off power charges (40% MORE AoE per charge), and I wanted to see if I could clear maps with it wearing Voll's Protector and critting a lot, since that is what Blood Mage seems to be about. The only problem is, Voll's Protector cannot give me more than 1 power charge per cast of Bonestorm, which makes this 10 exalt purchase very bad. Nowhere on the armour, the description of Power Charges, the description of Bonestorm or anywhere else I could look does it say Power Charges can't be generated at a rate of over 1 per skill use. Is it a bug or an intended feature that is not mentioned anywhere? It's seriously not that strong with Bonestorm, I don't see why it would be limited to 1 per skill use if that is the wording on the item ("25% chance to gain a power charge on critical hit", literally 1:1).

I've noticed that as well. Frost wall linked with cascade has given me 3 charges when I cast it directly on enemies and it instantly breaks, I would assume Bonestorm is supposed to do the same with a single cast.

Just confirming I've experienced the same issue - is this intended or actually a bug?