Whats odd is that when I navigate to the pro slide film page on the Kodak website its not their but when I search for it on the Kodak website I find a data sheet for it but it doesn't say its discontinued. I am struggling to find it in shops, is this still made, I was looking to get some for the purpose of cross processing. Is Elite Chrome 400 the same emultion?

400X was discontinued around 6 months ago, back when they discontinued some other Ektachromes.

I don't know how similar or dissimilar Elite Chrome 400 is, but I do know that Elite Chrome 400 is apparently also no longer made. There was no announcement, however it's not on Kodak's site any more.

Is faster slide film not very popular generally, as the fastest is now Provia 400X?

Provia 400X pushes very well. Even 3 stop push is not useless. A very impressive film!