2D glasses work by having the same direction polarisation lens in both eyes, letting people who normally get headaches from 3D films, watch 3D glasses with friends (obviously, if they're on their own they can just go watch 2D movies)
However on the purchase page they say:
Note: 2D glasses work in 3D cinemas. However, they do not work at IMAX theatres.
Why is that? What makes IMAX cinema 3D different?