King having Lunarian durability makes it harder to penetrate him and he poses higher resistance.
There is blood where Aramaki pierces King, he’s squeezing him to drain his energy and allow a more smooth sucking.
It makes no sense for the vines to drain from the outside, even less for a lunarian to not resist that.
Haki that makes wood strong wnough to penetrate a lunarian, that‘s why Aramaki does actually have a black blade. Without tp of the verse CoA his devil fruit is basically useless when you think about it.