Looks like Oda used the Ryuma symbolism against King's final attack, so it's probably Oda's own way to compensate with Luffy ultimately taking over the show versus Kaido
In the end still a bit disappointed that Oda covered the face reveal, flashback with Kaido, discovery of the weakness in King's ability and the final clash in a single chapter, but the chapter was so amazing that it compensates it, with some interesting dialogs
Guess this is Oda's way to increase the threat lvl of the battle by showing that it was a all or nothing kind of ending chapter due to Enma's drawbacks. In the end, while it allows you to create powerful haki enhanced attacks, you must still pay attention in finishing your opponent as fast as possible to avoid when Enma is fully released
Here we can now understand why Kaido gave him the name King. He saw strong potential in him, making him as his right hand man in order not to leave him to anyone else
This part suggest there is a moment when you need to attack King, making him more vulnerable to attacks at that point
And there is this interesting part as well thar seems to be in correlation with their earlier dialog about Zoro wanting to become a King. It seems that after hearing Zoro's attack name, it got King angry to the point he had to make Zoro remember that it won't be him, but Kaido who will be PK
Funny because it implies that he thinks the King Zoro wants to be is "Pirate King" lol
On a side note, it's interesting that Oda incorporated a fire manipulation that can apparently reach magma lvl in terms of heat. Guess it's a way to indirectly show the potential of the Mera Mera no mi