I can see the benefit for when different groups of Wikipedia editors have differing policy opinions where for an average user both the fork and the original are perfectly fine but now information is in both places or worse some in one and some in the other, especially for cross linking purposes. Wikipedia can hyperlink to wookiepedia for star wars stuff and wookiepedia can hyperlink to the aaroads wiki when referencing highways for example. It all become one much larger wiki effectively.

On the other hand, part of the draw of Wikipedia is the extremely high editing and page creation standards that has led to such a high quality source of information

Edit to add a positive and a negative:

I can see a federated wiki being very good for project wikis especially when linking to other projects, as well as for some level of redundancy

But also this is being developed by one of the 2 Lemmy developers, who still haven't implemented many of the needed moderation and administration tools for Lemmy