To me the value here is not that GPT4 has some special insight into explaining the behavior of GPT2 neurons (they say it's comparable to "human contractors" - but human performance on this task is also quite poor). The value is that you can just run this on every neuron if you're willing to spend the compute, and having a very fuzzy, flawed map of every neuron in a model is still pretty useful as a research tool.

But I would be very cautious about drawing conclusions from any individual neuron explanation generated in this way - even if it looks plausible by visual inspection of a few attention maps.