A suggestion would be to use the hook useInstantSearch (documentation here). Using this hook, you can access the stats for any Index in an isolated component. Dhaya from our team had this example which shows how to implement this hook:
Also, for useStats (or useHits) to grab the right Index’s information, it would have to be referenced from within a child component of the Index of interest. By default, if these hooks are not used within an Index it will inherit the main Index from the InstantSearch widget. This is also why you’ll see he removed the first <Index> element in his sandbox above.