Apollo Federation @shareable directive return inconsistent data?

As mentioned in the doc, while using @shareable directive, resolver consistency needs to be ensured.

Does that mean that the resolution of the shareable field can be from any of the subgraph? Do I need return identical response from all the subgraphs?

I tried reproducing the inconsistent behaviour, but the resolution was always from the correct subgraph in my case. Can you point me to some example in which the data can be inconsistent?

Thanks in advance