He didn't push for this, but he was tasked to see Partition through, and he bungled the job, hence "non- guidance". Maybe no fault of his, but you can get a deeper nuance of the larger issues at play by thinking about how he personally could have otherwise done an okay job. Taking the maxim to not assume malice to its pedantic conclusion. Plus, it's easier to think about a constrained space of individual actions and intentions even if the wider politics are so complex.

At that moment in time, Mountbatten was perhaps the personification of the Crown (and he would have known it)