When I created a new world in this snapshot, it asked me to press E to open my inventory. I did it, and I got the achievement, but it didn't tell me I got the achievement nor did the dialog saying "Press E to open your inventory." I tried reloading the world and pressing E a few more times, it still wouldn't go away.

I'm not sure if I did this or not, but I MAY have made the world name the same as a previous one that was already deleted.