Penance Brand Energy Bug

If my understanding of the changes are correct, there is a bug with penance brand reaching maximum stages.

As I understand the changes, penance brand no longer has an attached duration, and instead will explode when it reaches maximum energy.

In my build I have attached penance brand to swiftbrand as this should just now function as a more multiplier to its speed of explosion, and be agnostic to the attachment duration.

However, during my gameplay I am seeing two different outcomes based on my gameplay.

Scenario A:

I cast a penance brand on an enemy, after a short duration it explodes for a moderate sized AoE.

Scenario B:

I cast a penance brand on an enemy, I then cast wave of conviction, killing the enemy before the brand explodes. The brand then detaches, reattaches to a new enemy, charges further and explodes for a massive AoE (bigger than the screen).

This behaviour leads me to believe that a penance brand cast alone on a target is not reaching maximum charge and that when it detaches in scenario B, it retains it's charge and charges further when it reattaches, resulting in a proper 20 energy explosion.

I have tried to stack cast speed to "beat" the swiftbrand timer, but it is difficult to tell whether or not it makes a difference.

For bug recreation purposes, my character Omniciru is the character experiencing this behaviour.

Same problem.
Sometimes the aoe is little, sometimes it is huge.
The thing is, the gem description doesn't mention any AoE modifier related to energy stack or damage dealt.

I'm using brandsurge to further accelerate explosion, but it is awfully random.