While there is authority for the idea that a motion to dismiss can be converted to a motion for summary judgment, there is no authority for the opposite, as the cour would be sua sponte lowering the threshold requirements for the movant -- the fact that a cucumber can be made into a pickle doesn't necessarily mean that a pickle can be turned into a cucumber.
District court correctly construed the allegation of misrepresentations in the amended complaint to be a claim for fraud in the inducement (dolo), and correctly applied the sophisticated purchaser defense to determine that the purchaser's reliance was not reasonable.