This is an awesome bug that changes the texture depending on what boots you have on.

I was expecting the normal elytra skin should be on my back.

The texture of the Elytra was changed depending on what boots I have on.

Steps to Reproduce:
1. Put an Elytra on.
2. Press F5
3. Examine
4. Put boots on; any type should do.
5. Examine
6. Take off the boots and enchant them with whatever you wish.
7. Put on the boots
8. Examine