Luffy's power is still Toon Force, not Reality Warping. If he can make his imagination into reality, why hasn't he imagined Ace back into the living reality?
So far, he can shape anything within the physical existence into something else, which is good, but still not RW.
Look at this encounter below between Lucifer Morningstar and Silk Man, an Immortal Sorcerer, for an example of Reality Warping:
Lucifer simply willed Silk Man to be gone from existence, so Silk Man is gone because the reality that is Silk Man is molded into nonexistence. Now THAT'S called Reality Warping.
If Luffy had simply erased Kaido or Lucci from existence or, I don't know, turn them into dolls or paintings simply by forcing his imagination to alter the reality that are Kaido and Lucci, I would have conceded to your point. But Luffy didn't display any of those, so...