Why do wavwrite and audiowrite produce different results?

I am transitioning from wavwrite to audiowrite and encountered the problem that wavread and audioread do not always produce identical wav files. For example the code

    y = repmat((1:750)', 1, 3);
    wavwrite(y, 500, 32, 'test1.wav');
    audiowrite('test2.wav', y, 500, 'BitsPerSample', 32);

    fid = fopen('test1.wav');
    test1 = fread(fid);
    fclose(fid);
    fid = fopen('test2.wav');
    test2 = fread(fid);
    fclose(fid);

    length(test1)
    length(test2)

returns 9044 and 9096. Why is that and how can I reproduce the results from wavwrite in my existing code with audiowrite?

PS: I am aware of audioread, but that is not an option here.