The code in question:

case VECTOR_OP_UMIN: return (v, m) -> toBits(v.rOp(MAX_OR_INF, m, (i, a, b) -> (int) VectorMath.minUnsigned(a, b)));

Unfortunately, we are sloppy here, the identity value for UMIN should be -1 (MAX_UINT). I wonder why the tests do not catch it.