The 10x10 aspect of it appears to be because there's an invisible outer ring of "if your piece moves here, it is removed from the game" which wouldn't be possib

The 10x10 aspect of it appears to be because there's an invisible outer ring of "if your piece moves here, it is removed from the game" which wouldn't be possible with an 8x8 board that doesn't have an "outside". If you play the game, you'll see an 8x8 board.