With some quick testing it does seem to do so but I'm confused at this quotefrom the docs:

This is handy when you want to pass some state to an external library or API that doesn’t expect a proxy, such asstructuredClone.

If it already does deep clone the object, then why would you want to pass a snapshot tostructuredClone? Or is it more likestructuredClone is just an example for an API that doesn't expect a proxy? I don't know if I'm missing something here.