Notice the documentation for surf states that input argument X is "x-coordinates, specified as a matrix the same size as Z, or as a vector with length n, where [m,n] = size(Z)" and Y is "y-coordinates, specified as a matrix the same size as Z or as a vector with length m, where [m,n] = size(Z)". In other words, when using vector inputs as X and Y, the number of elements of X must be the same as the number of columns of Z and the number of elements of Y must be the same as the number of rows of Z. So surf interprets Z as having Y along the first dimension (down) and X along the second dimension (across).
In this case, the number of elements of X and Y are the same, so it's not obvious, but if you try it with say, x = [0:5]; y = [0:10]; surf(x,y,zeros(6,11)); you'll get an error because the third argument must be of size 11-by-6, i.e., you must do surf(x,y,zeros(11,6)); in that case.
All that is to say: transpose your matrix in the call to surf, and it'll work:
