If the merchant provides NULL shipping options, the merchant needs a     
shipping address to calculate shipping costs. The UI requires the user   
to make an address selection and passes that information to the          
merchant.                                                                
                                                                         
If the merchant provides non-NULL shipping options, the merchant does    
not need shipping address to calculate shipping costs. The UI selects    
the default shipping address, but does not send it to the merchant until 
the user clicks "Pay".

This is an Android bug, as this is the first platform with PaymentRequest UI.