The difference as I understand it is that the frames in-between the real frame are generated by extrapolation in the Frame Generation technologies. They use one of the many flavors of AI to do this.
The TV's Motion Smoothing is interpolation (which is fine for Movies) as there is no latency to be "felt".
Because I like to see the art that the game artists made, not AI interpretation of what should be in-between the frames. I'm not hung up on framerate, as long as it's stable and above 30 I'm good.