30 pin eDP compatibility

Hi

So I'm looking for alternative 30 pin eDP screen while I wait for the official version. I'm a little confused why the LP 7" screen does not work with the LP delta 3.  The pin outs are the same.  Is it some kind of protocal difference? Do they need special drivers or something? 

Is it fair to say not all 30 pin eDP protocols, hardware and screens are the same? If so, what are the exact requirements for an LP delta 3 eDP screen.

Thanks

Rich