Except, a machine CAN be truly random if you use something from outside the machine as a seed for the equation: http://www.random.org/randomness/
For instance, Grumpy could capture your mouse placement over the random button on the time of the click, do a modulus of which pixel you were on with the current Unix time and get a truly random number.
That ISN'T how he does it, but it was an example.
As for whether or not it's a "useful" enough feature, that has to be decided by Grumpy as stated before.
That still won't be truly random (and anyway it uses external influence) all you are doing is feeding more information to the seed for the algorithm, of course it won't be possible for a human to predict the result, but it still won't be absolute random... anyway I only mention it because people are talking about how excluding a genre would make it not truly random, but whenever the option gets implemented the randomness of the button won't change a bit.
Back on topic, it IS a useful feature, and without it the random button is but a decoration for many of us since we get a shoujo every 7 out of 10 times.. now of course, whenever it is enough to get accepted, yes, it is up to him.