You don't need to have black swords to be using haki. There are countless examples of this INCLUDING SCABBARDS VS KAIDO.
Additionally, you can look at it in two ways.
Either Luffy and Zoro/Killer both made him bleed or neither made them bleed. I think the former makes more sense considering Luffy JUST made him bleed last chapter with a G3 attack.
The visual indications for both attacks are the same.
Pretty much, the rooftop 5 is gonna use their known strong moves and they're gonna progressively use better and better attacks until they reach their best attacks that we know so far. Then they'll display new improved attacks.