Exploration Maps with different numbers should lead to different structures

Steps to reproduce:

1. Breed villagers until you get two cartographers
2. Trade with the cartographers until they each have a Woodland Explorer available for trade (make sure they are different # maps)
3. Trade for the Woodland Explorer maps

Expected results:

Each Woodland Explorer map is unique

Actual results:

Woodland Explorer maps, despite having unique numbers (in my case #64 and #69) appear to be identical (see screenshots attached)

World seed number: -6546044224551629769
This is on a hosted realm which was created September 4th 2014, which was Minecraft version 1.8 (I believe).