That is not a plane if you look close. That is thieving. The board layout had no copper there, but this can make the plating process more difficult to get consistent across the board. Usually this is added by the fab house to help them manufacture the board.

Exactly what I did. I went for the 1tb though. The storage prices for the deck are pretty outrageous and upgrading is pretty easy. So a 64gb deck + 1tb card comes out to be about the same as a 256gb deck.