There is a difference.
A ChessBoard assumes that the location of the king will be frequently queried.
As it stands now, our "Chessboard" has no functionality.
I do not want to add this "Find the king" function to my current "ChessBoard".
I've been writing this program with an eye to make the underlying game flexible enough to play checkers, if need be.
In checkers, there's no need to find the king.