I'm referring to dialouge by Luffy himself. This doesn't have to do with what we as readers know.
Here, let me put it this way: Impact Dials did get the "but I'm rubberman" dialog. Ambition hits get the "but I'm rubber" dialog. If Rokuougan makes Luffy think of the Impact Dial, then Luffy is indirectly thinking "but I'm rubber" because the Impact Dial made them think "but he's rubber". The only difference is that, at the time of the Impact Dial, there was nothing to relate the attack to, while Lucci's Rokuougan had the visual advantage of recalling the recently used Impact Dial.
However, during his fight with Lucci when the latter managed to hurt him using things like Rokuougan nothing like "how's he hurting me I'm a rubberman" was even mentioned, instead we got that it feels like an Impact Dial but stronger.
Lucci stated that a true master of all 6 forms could achieve Rokougan. If Tekkai is based on haki, and a mastery of it is necessary to pull off Rokougan, then logically Rokushiki utilizes a combination of both physical techniques and some form of haki.
Aside from nostalgia and a quick laugh at remembering how the conversation went, I pulled up Urouge's quote for a reason. You agreed on the principle but in the end doubted it because of the Impact Dial argument. Looking at my above argument, the reactions are synonymous due to the original Impact Dial scene. I don't see any reason to doubt it now, though I'm still not saying it is without a doubt Ambition. Rather, if it isn't using Ambition in some way, how is he doing it?