This would be very useful in scenarios where you want to utilize the reducability properties of minhash. One example is dealing with hierarchical data; the signature of a parent node can then be calculated as the element-wise minima combined signatures of all its child nodes, allowing two parents to be efficiently compared for similarity.
(This can of course be done by calling code since the MinHash class exposes the signature, but it would be convenient if this was provided as a static method on the MinHash class itself.)