Can I connect two 34" LG 34UM95-P to a Retina Macbook Pro 13?
You ABSOLUTELY can do this.  

The statement on the box is wrong. You can use either two mini-display port to displayport cables, or two Thunderbolt cables.

My statement was based on the fact that you can (according to Apple's documentation) run two Thunderbolt monitors on that laptop, and the available resolution on the Thunderbolt cable is clearly capable of 3440x1440.