On my desktop it picks up the desktop variant. On my ipad it picks up both the portrait & landscape versions correctly. On my mobile (HTC Android) it picks up the phone vertical okay but picks up the iphone horizontal when rotated.

However Xara sites aren't truely responsive, just giving various fixed sized versions. Not even sure if they can determine which mode the appliance is in, landscape or portrait (But in your example it appears to work for the ipad). Not really my area of expertise however.