Minecraft does expand 2560 x 1440

This has bugged me for a long while. I launch Minecraft (Effects all versions I believe, click play, and when it loads at the home screen I push the Expand icon in the top right hand corner, and the whole screen turns black, and in the bottom left hand corner I see a small snippet of the background of the home screen.

Can you please fix this? I can expand it somewhat, but not as far as I would like.