When is "Real 3D" not real 3D?

Never, actually.
"Real 3D is the technical process of taking films shot in normal 2D and technically converting them to look like 3D; a process doomed to failure. Basically it is like Decoupage: You take a flat picture, cut out bits of it, and arrange the bits at different distances from the background, to create an illusion of depth.
That's what they did with ALICE IN WONDERLAND, CLASH OF THE TITANS, and now the latest HARRY POTTER, which they are now not going to release in Decoupage 3D just yet, because they haven't finished cutting out all the bits.
Decoupage 3D looks dreadful. Characters and objects are placed at different distances, but the characters and objects are still flat, like cardboard cutouts. This type of 3D will turn audiences against the whole idea of 3D; even though movies actually shot in 3D, like AVATAR, are breathtakingly beautiful to watch.

The only way to make 3D movies is to shoot them in 3D in the first place.
Anything else is arrogant nonsense.