Actually, a lot of sound leakage from closed headphones are due to fit issues with certain people. The W5000 for example either leaks like crazy or not much at all, depending on the seal. The headphone wires can be adjusted to fit properly with a little bending. Same for the W1000X and W3000ANV.
Really, Audio-Technica makes more closed headphones than they do open ones. There's also the JVC Victor HP-DX1000 and 700, as well as the vastly underrated Kenwood K1000s. Ultrasone also just announced the Signature Pro, which is basically the spiritual successor to the Edition 9. Also what about the Beyerdynamic DT 1350, T70P, and T5P? Then there's the Sony Z1000 and ZX700...
To say that all of these aren't legitimate as closed headphones is kind of a sweeping generalization. People are going to have different shaped heads, and while some of them may not isolate well for one person, they may isolate much more effectively for another. In the end, all closed headphones are going to leak. It's just a matter of how much and the threshold of acceptability.