Zhuangzi and Huizi on the bridge: doubt about other minds, or a joke?

Every morning after taiji I sit by the river in the park, and this story comes back to me. It is in the "Autumn Floods" chapter of the Zhuangzi.

Zhuangzi and his friend Huizi are strolling on a bridge over the Hao river. Zhuangzi says: the minnows swim about so freely, this is the happiness of fish. Huizi, the logician, says: you are not a fish, so how do you know the happiness of fish? Zhuangzi says: you are not me, so how do you know I don't know the happiness of fish? Huizi says: I am not you, so I certainly don't know you; and you are certainly not a fish, so the case is complete, you don't know the happiness of fish. Zhuangzi says: let us go back to where we started. When you said "how do you know the happiness of fish", you already knew that I knew it, and asked me how. I knew it from here, above the Hao.

The last move turns on a pun. The question word can mean "how" and also "from where". Huizi asked how; Zhuangzi answers where.

So what is going on? It looks like the standard problem of other minds, local scepticism about the inner life of others. Huizi's argument would also cut between people, and Zhuangzi points that out. But Zhuangzi's final answer is not an argument. It is a joke, and also, I think, serious: knowing always happens from somewhere, from a standpoint, and asking for a knowledge from nowhere is the mistake.

My father kept this book on his shelf for forty years and I never opened it. Now I read this passage and cannot decide if Zhuangzi won or just changed the subject. I would like to hear how others read it.