Now I know NT normally does involve the full course of penetration, but consider also that the 'results' a dripping down on the outside of the opening in question, insead of out from the inside of said opening.
Of course; I wouldn't completely discount that the tentacle-creature's (a new kind of Neuroi?) pervertedness might extend to implantation in an alternate location to what is normally expected in NT.
Additionally; I wonder if this would qualify as vore, since Henrike seems to be inside the creature.