Breaking Ender Chest with Silk Touch

When you break an Ender Chest with normal pickaxe (with no enchant) you should get 8 Obsidian blocks, right? Yeah, and that works fine. Problem is, when you break your chest using Pickaxe with Silk Touch enchant. You should get full chest, right? Yup, but instead of getting only Ender Chest, you get Ender Chest AND 8 obsidian blocks. This is a bug, becouse you can literally clone your Obsidian.
I discovered this playing on Realms with my friends. Windows 10, 1.2.3

/Sorry for my English