It may go deeper than that though.
They are like Haki's Equivalent of Solid, Liquid & Gas
Think of it like Water & it's Three States
This Energy is basically your Willpower
But what if instead of changing it's States, you change the Source of this Energy
What if it's also Fueled by your Body? and what if it's fueled by your Emotions as well?
That means each Living Being can turn their Physical Power or their Emotions into Energy
Rokushiki was based on Physical Power (Doriki)
That's why it looked similar to Haki Techniques, such as Tekkai being like Hardening & Rokuogan being like Internal Destruction ... etc
So what's stopping Oda from making Emotions another Source of Energy/Haki/Willpower?
The Key to Damaging Gorosei imo is not about CoC or how Strong your Haki is, it's about including Emotions/Heart as it's Source
And that's what Sanji calls "Power of Love" & it manifests in form of Flames
Shanks Fights with a Flaming Sword, i believe it's based on this Skill, something that Zoro & Luffy need to learn Next
It's like your Haki turns from Water into Fire, and these Flames leave Permanant Injuries on Gorosei & also Yami Yami's Darkness