Anything that incorporates Force powers such as TK into lightsaber sequences is Niman by default. There's almost nothing else, fluff-wise, that it could be, since if other forms concentrated on developing such techniques, there would have been no need to develop Niman in the first place.
As for the special, I would go for spend a FP to knock the target prone. Makashi riposte allows you to spend a FP to take no damage instead of half damage because it's specifically a dueling style. Its focus is on bladework, and the special reflects that. Niman on the other hand is an all-purpose style with relaxed emphasis on bladework. Thus, IMO knocking the target prone (reflecting Niman's Force emphasis) would be better suited for Deflecting thrust.