You saying black lightning doesn´t mean a advanced form is not wrong, but you clearly forget that Katakuri mentioned a stronger haki form, where Luffy hand got damaged alone by hit Katakuri, same happen with Wsw this chapter. And both scenario looking the same, black lightning coming out from the CoA body part, this time overall around Jinbe since>full body haki.
You comment doesn´t make anysense in case, saying used black lightning is not the only argument here, you can clearly see based on the Katakuri statement that both he and Jinbe haki probably beeing in similar lvl, above the usually CoA.