Nah, there's black lightning:
You do have a point that there's much less haki enhancement than e.g. Kaido's Three World Ragnarok. Perhaps a stronger version is possible, but I'm not sure. This was still an attack the Yonkou used to try and kill the Roof Five in one shot. Before launching it, Kaido asks Mama if she's still in shape to perform it. I don't think they were holding themselves back when they used it.