There's three versions: 24FPS 2D, 24FPS 3D, and 48FPS 3D.

You most likely saw the 24FPS 3D version, unless it was specifically advertised as "HFR". The main aim of HFR is to make the 3D work better and not give the usual headaches, etc. people get when watching 3D.

I haven't actually seen the 24FPS version yet, but I imagine there's a possibility the 24FPS version has a much faster shutter speed than would typically be seen in a 24FPS movie, which could give it a 'poor fps'/jittery feel like that you experience in a PC game with low FPS.