Why does `minmax` take longer than a consecutive `min` and `max`?

Well basically the question says it all, my intuition tells me that a call to minmax should take less time than calling a min and then a max.

Is there some optimization I prevent Matlab carrying out in the following code?

minmax:

function minmax_vals = minmaxtest()
    buffSize = 1000000;
    A = rand(128,buffSize);
    windowSize = 100;
    minmax_vals = zeros(128,buffSize/windowSize*2);
    for i=1:(buffSize/windowSize)
        minmax_vals(:,(2*i-1):(2*i)) = minmax(A(:,((i-1)*windowSize+1):(i*windowSize)));
    end
end

separate min-max:

function minmax_vals = minmaxtest()
    buffSize = 1000000;
    A = rand(128,buffSize);
    windowSize = 100;
    minmax_vals = zeros(128,buffSize/windowSize*2);
    for i=1:(buffSize/windowSize)
        minmax_vals(:,(2*i-1)) = min(A(:,((i-1)*windowSize+1):(i*windowSize)),[],2);
        minmax_vals(:,(2*i)) = max(A(:,((i-1)*windowSize+1):(i*windowSize)),[],2);
    end
end