When Oda said I don't want Luffy to win JUST BECAUSE HIS PUNCH IS SO STRONG (literally what Kid just stated), and Luffy and I have to figure out a solution.
That's 100% "penetration" Haki. And that was in
2016.
Did he have some concept of flowing/advanced Haki in Sabaody? Yes. We saw Rayleigh/Admirals/Sento/Marigold. But this distinction of "penetration" from "flowing" was clearly a last minute addition in response to 2016 comments.
^ This 100% aligns with his comments exactly. And he only came up with this in the last 3 years or so.